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Record Attempt  Time Commenced  Personal Achievement 
1. 196 Palindrome Quest  August 4, 1999 
Former WORLD RECORD achieved September 6, 1999. Current WORLD RECORD achieved by Wade VanLandingham. 
2. Most Delayed Palindrome  August 13, 1999 
My First WORLD RECORD achieved September 3, 1999. My Latest WORLD RECORD achieved November 30, 2005. Current WORLD RECORD achieved by Rob van Nobelen (April 26, 2019). 
What is a Palindrome?
(The world's longest palindromic sentence, based on the timeless classic, "A man, a plan, a canal... Panama", has been created by Peter Norvig. For more word, sentence, and phrase palindromes, please visit Jim Kalb's Palindrome Connection.) 
196 PALINDROME QUEST 
Numeric Palindromes

Examples
In fact, about 80% of all numbers under 10,000 solve in 4 or less steps. About 90% solve in 7 steps or less. A rare case, number 89, takes 24 iterations to become a palindrome. It takes the most steps of any number under 10,000 that has been resolved into a palindrome:

The 196 Palindrome Quest (a.k.a. 196 Algorithm, 196 Problem)
The 1973 paper states that Harborth said that Trigg checked all integers less than 10,000 in 1967 and found that 249
seemed to never form a palindrome. 196 would be the first of those 249 numbers. 
"The work you refer to was done about 20 years ago on a 4 MHz Z80based machine running CP/M. The core reverse&add and the palindromicity detector were written in assembler and the I/O etc was written in Algol60. The machine only had 32K of memory (actually rather a lot for those days) and I ran the program until it ran out of memory  which explains the limit chosen for the number of iterations."  Paul C. Leyland 
Again, P. Anderton continued the process up to 70,928 digits (170,000+ iterations) without encountering a palindrome. (This Google Groups posting claims a 70,000 digit result was accomplished in 1987, so perhaps this was P. Anderton's effort.) 
The First Iterations of 196 
Three Years of Computing (196 taken to 1,000,000 digits) 
About Two Months of Computing (from 1,000,000 to 2,000,000 digits) 
Continuing the Quest (to 13,000,000 digits and beyond)
The program reached the 5,000,000 digit mark in an additional 13 days and 8 hours. The program is now running solely on the Celeron 400 MHz processor. The program reached the 6,000,000 digit mark in an additional 14 days and 4 hours. The program reached the 7,000,000 digit mark in an additional 26 days and 12 hours. The program reached the 8,000,000 digit mark in an additional 33 days and 23 hours. The program reached the 9,000,000 digit mark in an additional 59 days and 12 hours. (The increased length of time for this million digits is probably caused by the fact that the program was stopped and continued very many times during this period.) The program reached the 10,000,000 digit mark in an additional 34 days and 1 hour. The program reached the 11,000,000 digit mark in an additional 26 days and 3 hours. The program reached the 12,000,000 digit mark in an additional 28 days and 5 hours. The program reached the 13,000,000 digit mark in an additional 28 days and 23 hours. (The program had a little help of a Pentium III 450 MHz machine for this million digits, although the program can only be run on one machine at any given time.)
The program was averaging over 12,000,000 single digit additions per second
with the Celeron 400 MHz machine
(i.e. it can add two 12,000,000 digit numbers in one second).
That's over 1 trillion (1,000,000,000,000) single digit additions per day. 
Other Work  Ian J. Peter 
Other Work  István Bozsik 

196 Discussion  Message Board

MOST DELAYED PALINDROMIC NUMBER 
The Previous Record

The Procedure

Thoughts on Improving the Search 
Improving the Search 
Implementing the Search
FRIDAY, AUGUST 4, 2000 UPDATE: More statistics of the program follows: 
Jason's New Exponential Algorithm Performance (AMDK6 200 MHz) 

It solved all 6 digit numbers and below in 1 second. It solved all 7 digit numbers in 28 seconds. It solved all 8 digit numbers in 1 minute 38 seconds. It solved all 9 digit numbers in 21 minutes 51 seconds. It solved all 10 digit numbers in 59 minutes 16 seconds. It solved all 11 digit numbers in 20 hours, 29 minutes. It solved all 12 digit numbers in 1 day, 20 hours. It solved all 13 digit numbers in 31 days, 9 hours. It solved all 14 digit numbers in 63 days, 9 hours. It solved 8.34% of all 15 digit numbers. 
At this point, the program stopped due to lack of a computer to run the program. 
The Results
Also, later that day, at 7:28 PM, a record for 160 iterations was found:
10,019,017,999,499,510.
It is lower than the number that we expected could be the potential record
(14,200,033,399,975,995),
and it is on a different thread (series of numbers that are formed by the reversaladdition iteration),
as the resultant palindrome is different from that of
the record for 161 iterations.
(Please note that on January 28, 2004, an even smaller number for 160 iterations was found,
on yet another thread:
10,000,000,730,931,027.)
WEDNESDAY, DECEMBER 15, 2004 UPDATE:
MONDAY, MARCH 21, 2005 UPDATE:
You will note that this data is not immediately known from the
records I show on this page.
My Most Delayed Palindromic Number quest
stores only the smallest number that resolves at each iteration depth.
Therefore if a record is set in a smaller digit set,
any other numbers that resolve in the same amount of iterations from
larger digit sets will not be recorded, since they are larger numbers.
These numbers are not recorded even if they are the
most delayed palindromic number of that digit set, simply because
this was not the purpose of the program.
(Please note the above data is obtained from the subset of numbers my program tests. My program does not test every number, due to the optimizations explained earlier. So, while this graph is not 100% accurate, it is certainly very close. Most likely, it is accurate to well within the precision shown.)

Most Delayed Palindromic Number Records 
Solved all 1 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
1 5 
1 2 
1 2 
2 11 
Solved all 2 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
59 69 79 89 
3 4 6 24 
4 4 5 13 
1111 4884 44044 8813200023188 
Solved all 3 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
166 188 193 829 167 849 177 999 739 989 869 187 
5 7 8 10 11 14 15 16 17 19 22 23 
5 6 6 8 8 10 10 10 10 11 13 13 
45254 233332 233332 88555588 88555588 8836886388 8836886388 8939779398 5233333325 89540004598 8813200023188 8813200023188 
Solved all 4 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
1,397 2,069 1,797 1,798 6,999 1,297 
9 12 13 18 20 21 
8 8 10 11 14 13 
88555588 52788725 8836886388 89540004598 16668488486661 8813200023188 
Solved all 5 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
10,797 10,853 10,921 10,971 13,297 10,548 13,293 17,793 20,889 80,359 13,697 10,794 15,891 70,759 70,269 10,677 10,833 10,911 
25 26 27 28 29 30 31 32 33 37 38 39 40 47 52 53 54 55 
16 16 16 16 18 17 17 17 17 22 22 22 22 26 28 28 28 28 
1676404554046761 4455597447955544 4455597447955544 8802202552022088 893974888888479398 17858768886785871 17858768886785871 44035358885353044 44035358885353044 6839849878998789489386 6839849878998789489386 6832123695335963212386 6832123695335963212386 14525756544499444565752541 4668731596684224866951378664 4668731596684224866951378664 4668731596684224866951378664 4668731596684224866951378664 
Solved all 6 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
700,269 106,977 108,933 600,259 131,996 600,279 141,996 600,579 147,996 178,992 190,890 600,589 150,296 
34 35 36 45 46 50 51 57 58 59 60 63 64 
22 22 22 26 26 28 28 31 31 31 31 33 33 
6832123695335963212386 6832123695335963212386 6832123695335963212386 14525756544499444565752541 14525756544499444565752541 4668731596684224866951378664 4668731596684224866951378664 8834453324841674761484233544388 8834453324841674761484233544388 8834453324841674761484233544388 8834453324841674761484233544388 682049569465550121055564965940286 682049569465550121055564965940286 
Solved all 7 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
1,009,227 1,007,619 1,009,246 1,008,628 1,007,377 1,001,699 1,009,150 1,058,921 1,050,995 1,003,569 1,036,974 1,490,991 3,009,179 1,008,595 1,064,912 1,998,999 7,008,429 1,000,689 1,005,744 1,007,601 7,008,899 9,008,299 
41 42 43 44 48 49 56 61 62 65 66 67 68 69 70 75 77 78 79 80 82 96 
23 22 23 23 28 27 28 32 33 32 32 32 35 35 35 32 38 39 39 38 38 48 
68344497279697279444386 1556534287227824356551 45144454432023445444154 48852787646664678725884 8836746997299229927996476388 168977944479424974449779861 6842165664428668244665612486 18966336852467966976425863366981 682049569465550121055564965940286 14758724578598888889587542785741 14758724578598888889587542785741 14758724578598888889587542785741 46563056797844547874544879765036564 46563056797844547874544879765036564 46563056797844547874544879765036564 15521561387579888897578316512551 14674443960143265333356234106934447641 796589884324966945646549669423488985697 796589884324966945646549669423488985697 14674443960143265333356234106934447641 68586378655656964999946965655687368586 555458774083726674580862268085476627380477854555 
Solved all 8 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
10,905,963 10,069,785 10,089,342 11,979,990 10,029,372 10,029,826 16,207,990 90,000,589 10,309,988 
71 72 73 74 76 81 83 94 95 
38 32 32 32 39 38 38 48 48 
35695487976778433588533487767978459653 15521561387579888897578316512551 15521561387579888897578316512551 15521561387579888897578316512551 796589884324966945646549669423488985697 68586378655656964999946965655687368586 68586378655656964999946965655687368586 555458774083726674580862268085476627380477854555 555458774083726674580862268085476627380477854555 
Solved all 9 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
100,389,898 100,055,896 110,909,992 160,009,490 800,067,199 151,033,997 100,093,573 103,249,931 107,025,910 180,005,498 100,239,862 140,669,390 
84 85 86 87 88 89 90 91 92 93 97 98 
45 41 40 40 46 46 46 46 46 48 52 52 
584227988787668589199242991985866787889722485 88682199585544879735653797844558599128688 3525698275220268897227988620225728965253 3525698275220268897227988620225728965253 5852497685678899643696996963469988765867942585 5852497685678899643696996963469988765867942585 5852497685678899643696996963469988765867942585 5852497685678899643696996963469988765867942585 5852497685678899643696996963469988765867942585 555458774083726674580862268085476627380477854555 1345428953367763125675365555635765213677633598245431 1345428953367763125675365555635765213677633598245431 
Solved all 10 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
1,090,001,921 7,007,009,909 1,009,049,407 9,000,046,899 1,050,027,948 1,304,199,693 5,020,089,949 1,005,499,526 
99 100 101 103 104 105 108 109 
46 49 49 49 49 49 53 53 
6634544448788301675886446885761038878444454366 1543434266587555114779722279774115557856624343451 1543434266587555114779722279774115557856624343451 5831124885795990016569666669656100995975884211385 5831124885795990016569666669656100995975884211385 5831124885795990016569666669656100995975884211385 66330069478378985774345546664554347758987387496003366 66330069478378985774345546664554347758987387496003366 
Solved all 11 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
10,000,505,448 10,000,922,347 10,000,696,511 10,701,592,943 10,018,999,583 10,000,442,119 10,000,761,554 10,084,899,970 10,006,198,250 18,060,009,890 11,400,245,996 16,002,897,892 18,317,699,990 37,000,488,999 10,050,289,485 90,000,626,389 10,000,853,648 13,003,696,093 10,050,859,271 10,287,799,930 10,000,973,037 10,600,713,933 10,942,399,911 60,000,180,709 11,009,599,796 16,000,097,392 10,031,199,494 10,306,095,991 10,087,799,570 
102 106 107 110 111 112 113 114 115 116 117 118 119 122 123 130 131 132 133 134 135 136 137 144 145 146 147 148 149 
49 50 56 53 56 56 56 56 56 56 56 56 56 58 58 65 65 65 65 65 71 71 71 66 66 66 66 66 66 
5831124885795990016569666669656100995975884211385 15739929700341113302426977962420331114300792993751 13323895762789854121576789855898767512145898726759832331 23103742208899345951210026862001215954399880224730132 13656852665688105699133698688689633199650188656625865631 13656852665688105699133698688689633199650188656625865631 13656852665688105699133698688689633199650188656625865631 13656852665688105699133698688689633199650188656625865631 13656852665688105699133698688689633199650188656625865631 15997773553851169652456786055068765425696115835537779951 11144565886884377368565136533563156586377348868856544111 11144565886884377368565136533563156586377348868856544111 11144565886884377368565136533563156586377348868856544111 4618999883854436730489915000000005199840376344583889998164 4618999883854436730489915000000005199840376344583889998164 12346788678755866852059426528989698982562495025866855787688764321 12346788678755866852059426528989698982562495025866855787688764321 12346788678755866852059426528989698982562495025866855787688764321 12346788678755866852059426528989698982562495025866855787688764321 12346788678755866852059426528989698982562495025866855787688764321 12366212267356333541465465587987721212778978556456414533365376221266321 12366212267356333541465465587987721212778978556456414533365376221266321 12366212267356333541465465587987721212778978556456414533365376221266321 895549975467412444422685224544649946445422586224444214764579945598 895549975467412444422685224544649946445422586224444214764579945598 895549975467412444422685224544649946445422586224444214764579945598 895549975467412444422685224544649946445422586224444214764579945598 895549975467412444422685224544649946445422586224444214764579945598 895549975467412444422685224544649946445422586224444214764579945598 
Solved all 12 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
100,900,509,906 100,000,055,859 104,000,146,950 180,005,998,298 300,000,185,539 100,001,987,765 
120 121 124 129 142 143 
58 58 58 65 66 66 
4618999883854436730489915000000005199840376344583889998164 4618999883854436730489915000000005199840376344583889998164 4618999883854436730489915000000005199840376344583889998164 12346788678755866852059426528989698982562495025866855787688764321 895549975467412444422685224544649946445422586224444214764579945598 895549975467412444422685224544649946445422586224444214764579945598 
Solved all 13 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
1,000,007,614,641 1,000,043,902,320 1,000,006,653,746 1,000,005,469,548 4,000,096,953,659 1,332,003,929,995 1,000,201,995,662 6,000,008,476,379 1,200,004,031,698 1,631,002,019,993 1,000,006,412,206 1,090,604,591,930 1,600,005,969,190 
125 126 127 128 139 140 141 183 184 185 186 187 188 
65 65 65 68 66 66 66 87 87 87 87 87 87 
68236478976724413455368469647845654874696486355431442767987463286 68236478976724413455368469647845654874696486355431442767987463286 12346788678755866852059426528989698982562495025866855787688764321 46476268994355205755566889613764755746731698866555750255349986267464 895549975467412444422685224544649946445422586224444214764579945598 895549975467412444422685224544649946445422586224444214764579945598 895549975467412444422685224544649946445422586224444214764579945598 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 
Solved all 14 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
10,090,899,969,901 40,000,004,480,279 14,104,229,999,995 
138 181 182 
70 87 87 
2319937995996732122112578857767863993687677588752112212376995997399132 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 
Solved all 15 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
100,000,109,584,608 100,000,098,743,648 100,004,789,906,151 100,079,239,995,161 100,389,619,999,030 200,000,729,975,309 107,045,067,996,994 105,420,999,199,982 101,000,269,830,970 104,000,047,066,970 700,000,001,839,569 100,000,050,469,737 101,000,789,812,993 100,907,098,999,571 100,017,449,991,820 890,000,023,937,399 100,009,989,989,199 101,507,024,989,944 107,405,139,999,943 100,057,569,996,821 103,500,369,729,970 900,000,076,152,049 100,000,439,071,028 120,000,046,510,993 103,000,015,331,997 100,617,081,999,573 100,009,029,910,821 107,000,020,928,910 100,000,090,745,299 102,000,149,322,944 130,000,074,931,591 100,120,849,299,260 
150 151 152 153 154 155 156 157 158 159 163 164 165 166 167 169 170 171 172 173 174 178 179 180 189 190 191 192 198 199 200 201 
80 73 80 73 73 77 77 83 77 83 78 78 77 77 77 80 76 76 82 82 80 87 87 87 87 87 87 87 92 92 92 92 
14751782101782013776625853112452243335411453334225421135852667731028710128715741 3874338821379754365139707922389885874785889832297079315634579731288334783 14751782101782013776625853112452243335411453334225421135852667731028710128715741 3874338821379754365139707922389885874785889832297079315634579731288334783 3874338821379754365139707922389885874785889832297079315634579731288334783 58432004534377668812885984239766675854845857666793248958821886677343540023485 58432004534377668812885984239766675854845857666793248958821886677343540023485 66364653972239888685894387234687476484136863148467478643278349858688893227935646366 58432004534377668812885984239766675854845857666793248958821886677343540023485 66364653972239888685894387234687476484136863148467478643278349858688893227935646366 177454986735997675255356985559732595246642595237955589653552576799537689454771 177454986735997675255356985559732595246642595237955589653552576799537689454771 15951239866387982563456955855439974585458547993455855965436528978366893215951 15951239866387982563456955855439974585458547993455855965436528978366893215951 15951239866387982563456955855439974585458547993455855965436528978366893215951 36764456433123268897359635569438786398655689368783496553695379886232133465446763 1685279897987756678784477446325846776116776485236447744878766577897989725861 1685279897987756678784477446325846776116776485236447744878766577897989725861 4973663467878710242597852762388983882088668802883898832672587952420178787643663794 4973663467878710242597852762388983882088668802883898832672587952420178787643663794 36764456433123268897359635569438786398655689368783496553695379886232133465446763 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 129816518702696188228910113874486338915527747725519833684478311019822881696207815618921 129816518702696188228910113874486338915527747725519833684478311019822881696207815618921 129816518702696188228910113874486338915527747725519833684478311019822881696207815618921 129816518702696188228910113874486338915527747725519833684478311019822881696207815618921 16616723795884852455598564101455698426624444977944442662489655410146589555425848859732761661 16616723795884852455598564101455698426624444977944442662489655410146589555425848859732761661 16616723795884852455598564101455698426624444977944442662489655410146589555425848859732761661 16616723795884852455598564101455698426624444977944442662489655410146589555425848859732761661 
Solved all 16 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
6,000,000,039,361,479 1,421,000,069,679,996 1,000,650,998,992,311 1,000,002,899,436,401 1,000,100,396,492,200 1,400,000,027,672,498 7,090,000,039,309,919 1,000,050,048,994,957 1,003,000,024,749,923 1,000,803,019,495,711 1,030,020,097,997,900 
161 162 168 175 176 177 193 194 195 196 197 
78 78 76 78 78 87 92 92 92 92 92 
177454986735997675255356985559732595246642595237955589653552576799537689454771 177454986735997675255356985559732595246642595237955589653552576799537689454771 1685279897987756678784477446325846776116776485236447744878766577897989725861 169635646445469964587742217600000453348843354000006712247785469964544646536961 169635646445469964587742217600000453348843354000006712247785469964544646536961 159788389444247969944047982661126897487188000881784798621166289740449969742444983887951 16616723795884852455598564101455698426624444977944442662489655410146589555425848859732761661 16616723795884852455598564101455698426624444977944442662489655410146589555425848859732761661 16616723795884852455598564101455698426624444977944442662489655410146589555425848859732761661 16616723795884852455598564101455698426624444977944442662489655410146589555425848859732761661 16616723795884852455598564101455698426624444977944442662489655410146589555425848859732761661 
Solved all 17 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
10,000,000,730,931,027 20,005,000,862,599,819 11,450,360,479,969,994 10,009,000,275,899,569 10,059,430,139,999,234 12,179,702,595,999,991 79,000,000,445,783,599 10,000,000,767,846,797 10,000,000,673,402,336 10,000,000,525,586,206 10,005,000,760,994,249 10,030,503,899,969,524 12,000,009,694,736,291 10,442,000,392,399,960 
160 206 207 208 209 210 229 230 231 232 233 234 235 236 
82 90 90 90 90 90 112 112 111 111 111 111 111 111 
1454578665279976634446532368777548944388998834498457778632356444366799725668754541 795884875720569937749728766349898266325776598895677523662898943667827947739965027578488597 795884875720569937749728766349898266325776598895677523662898943667827947739965027578488597 795884875720569937749728766349898266325776598895677523662898943667827947739965027578488597 795884875720569937749728766349898266325776598895677523662898943667827947739965027578488597 795884875720569937749728766349898266325776598895677523662898943667827947739965027578488597 4577267267265113973218923972796414755643668659429704525555254079249568663465574146972793298123793115627627627754 4577267267265113973218923972796414755643668659429704525555254079249568663465574146972793298123793115627627627754 579922447678688885254995975774499665520124525649777656969656777946525421025566994477579599452588886876744229975 579922447678688885254995975774499665520124525649777656969656777946525421025566994477579599452588886876744229975 579922447678688885254995975774499665520124525649777656969656777946525421025566994477579599452588886876744229975 579922447678688885254995975774499665520124525649777656969656777946525421025566994477579599452588886876744229975 579922447678688885254995975774499665520124525649777656969656777946525421025566994477579599452588886876744229975 579922447678688885254995975774499665520124525649777656969656777946525421025566994477579599452588886876744229975 
Solved all 18 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
195,030,047,999,791,993 100,000,078,999,111,766 100,710,000,333,399,973 100,000,002,973,751,552 100,000,277,999,334,202 110,300,361,999,869,090 300,000,000,128,545,799 104,300,000,514,769,945 100,700,000,509,609,622 120,906,490,499,909,290 900,040,000,881,499,569 100,072,100,489,999,238 121,506,542,999,979,993 106,096,507,979,997,951 100,980,800,839,699,830 600,000,000,606,339,049 170,500,000,303,619,996 
202 203 204 205 211 212 213 214 215 216 218 219 220 221 222 227 228 
105 105 90 90 107 107 101 101 101 101 103 103 103 103 103 112 112 
889956674896587435857678447634488652657823489664135444531466984328756256884436744876758534785698476659988 889956674896587435857678447634488652657823489664135444531466984328756256884436744876758534785698476659988 795884875720569937749728766349898266325776598895677523662898943667827947739965027578488597 795884875720569937749728766349898266325776598895677523662898943667827947739965027578488597 16625459966833465379947700047533357850265135989944697679644998953156205875333574000774997356433866995452661 16625459966833465379947700047533357850265135989944697679644998953156205875333574000774997356433866995452661 14884695685311269599498656858759854685128966643652225634666982158645895785865689499596211358659648841 14884695685311269599498656858759854685128966643652225634666982158645895785865689499596211358659648841 14884695685311269599498656858759854685128966643652225634666982158645895785865689499596211358659648841 14884695685311269599498656858759854685128966643652225634666982158645895785865689499596211358659648841 1596569934458730179488896975455653647842016863898846488983686102487463565545796988849710378544399656951 1596569934458730179488896975455653647842016863898846488983686102487463565545796988849710378544399656951 1596569934458730179488896975455653647842016863898846488983686102487463565545796988849710378544399656951 1596569934458730179488896975455653647842016863898846488983686102487463565545796988849710378544399656951 1596569934458730179488896975455653647842016863898846488983686102487463565545796988849710378544399656951 4577267267265113973218923972796414755643668659429704525555254079249568663465574146972793298123793115627627627754 4577267267265113973218923972796414755643668659429704525555254079249568663465574146972793298123793115627627627754 
As of Saturday, January 23, 2010, solved 55.011% of all 19 digit numbers  
Number  Iterations  Digits  Resultant Palindrome 
1,000,000,038,990,407,538 1,000,000,005,577,676,468 1,060,000,000,523,124,995 1,000,000,079,994,144,385 1,003,062,289,999,939,142 1,186,060,307,891,929,990 
217 225 226 259 260 261 
107 111 112 119 119 119 
49627604840136499793982885796699976479895651785665644844656658715659897467999669758828939799463104840672694 579922447678688885254995975774499665520124525649777656969656777946525421025566994477579599452588886876744229975 4577267267265113973218923972796414755643668659429704525555254079249568663465574146972793298123793115627627627754 44562665878976437622437848976653870388884783662598425855963436955852489526638748888307835667984873422673467987856626544 44562665878976437622437848976653870388884783662598425855963436955852489526638748888307835667984873422673467987856626544 44562665878976437622437848976653870388884783662598425855963436955852489526638748888307835667984873422673467987856626544 
Iterations up to 261 for which no number was found  
223, 224, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258. 
The intriguing part about these records is that it takes an unreal amount of calculations to discover them, but it takes only a minute amount of calculations to prove that they terminate with a palindrome in the claimed number of iterations. With a program, it would take less than one second to prove that the above numbers do indeed solve out. I do not need a Guinness World Records Official to be present during these calculations. You can take these numbers yourself, write up a quick program, and prove the results yourself. In fact, I have done so. Click on any of the numbers above, and you will be shown a calculation page  computed in realtime (you can test this by entering your own unique number at the end of the URL)  proving that this number resolves into a palindrome in the displayed number of steps, showing you the calculations required to get there. Please contact me if you would like more information, or if you know that I have stated incorrect information on this page. To the best of my knowledge, it is correct at this time.

Palindrome Integer Sequences



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