REVERSAL-ADDITION PALINDROME TEST ON 10018999583 Reverse and Add Process: 1. Pick a number. 2. Reverse its digits and add this value to the original number. 3. If this is not a palindrome, go back to step 2 and repeat. Let's view this Reverse and Add sequence starting with 10018999583: 10018999583 + 38599981001 step 1: 48618980584 + 48508981684 step 2: 97127962268 + 86226972179 step 3: 183354934447 + 744439453381 step 4: 927794387828 + 828783497729 step 5: 1756577885557 + 7555887756571 step 6: 9312465642128 + 8212465642139 step 7: 17524931284267 + 76248213942571 step 8: 93773145226838 + 83862254137739 step 9: 177635399364577 + 775463993536771 step 10: 953099392901348 + 843109293990359 step 11: 1796208686891707 + 7071986868026971 step 12: 8868195554918678 + 8768194555918688 step 13: 17636390110837366 + 66373801109363671 step 14: 84010191220201037 + 73010202219101048 step 15: 157020393439302085 + 580203934393020751 step 16: 737224327832322836 + 638223238723422737 step 17: 1375447566555745573 + 3755475556657445731 step 18: 5130923123213191304 + 4031913123213290315 step 19: 9162836246426481619 + 9161846246426382619 step 20: 18324682492852864238 + 83246825829428642381 step 21: 101571508322281506619 + 916605182223805175101 step 22: 1018176690546086681720 + 0271866806450966718101 step 23: 1290043496997053399821 + 1289933507996943400921 step 24: 2579977004993996800742 + 2470086993994007799752 step 25: 5050063998988004600494 + 4940064008898993600505 step 26: 9990128007886998200999 + 9990028996887008210999 step 27: 19980157004774006411998 + 89911460047740075108991 step 28: 109891617052514081520989 + 989025180415250716198901 step 29: 1098916797467764797719890 + 0989177974677647976198901 step 30: 2088094772145412773918791 + 1978193772145412774908802 step 31: 4066288544290825548827593 + 3957288455280924458826604 step 32: 8023576999571750007654197 + 7914567000571759996753208 step 33: 15938144000143510004407405 + 50470440001534100044183951 step 34: 66408584001677610048591356 + 65319584001677610048580466 step 35: 131728168003355220097171822 + 228171790022553300861827131 step 36: 359899958025908520958998953 + 359899859025809520859998953 step 37: 719799817051718041818997906 + 609799818140817150718997917 step 38: 1329599635192535192537995823 + 3285997352915352915369959231 step 39: 4615596988107888107907955054 + 4505597097018887018896955164 step 40: 9121194085126775126804910218 + 8120194086215776215804911219 step 41: 17241388171342551342609821437 + 73412890624315524317188314271 step 42: 90654278795658075659798135708 + 80753189795657085659787245609 step 43: 171407468591315161319585381317 + 713183585913161513195864704171 step 44: 884591054504476674515450085488 + 884580054515476674405450195488 step 45: 1769171109019953348920900280976 + 6790820090298433599109011719671 step 46: 8559991199318386948029912000647 + 7460002199208496838139911999558 step 47: 16019993398526883786169824000205 + 50200042896168738862589339991061 step 48: 66220036294695622648759163991266 + 66219936195784622659649263002266 step 49: 132439972490480245308408426993532 + 235399624804803542084094279934231 step 50: 367839597295283787392502706927763 + 367729607205293787382592795938763 step 51: 735569204500577574775095502866526 + 625668205590577475775005402965537 step 52: 1361237410091155050550100905832063 + 3602385090010550505511900147321631 step 53: 4963622500101705556062001053153694 + 4963513501002606555071010052263694 step 54: 9927136001104312111133011105417388 + 8837145011103311112134011006317299 step 55: 18764281012207623223267022111734687 + 78643711122076232232670221018246781 step 56: 97407992134283855455937243129981468 + 86418992134273955455838243129970479 step 57: 183826984268557810911775486259951947 + 749159952684577119018755862489628381 step 58: 932986936953134929930531348749580328 + 823085947843135039929431359639689239 step 59: 1756072884796269969859962708389269567 + 7659629838072699589699626974882706571 step 60: 9415702722868969559559589683271976138 + 8316791723869859559559698682272075149 step 61: 17732494446738829119119288365544051287 + 78215044556388291191192883764449423771 step 62: 95947539003127120310312172129993475058 + 85057439992127121301302172130093574959 step 63: 181004978995254241611614344260087050017 + 710050780062443416116142452599879400181 step 64: 891055759057697657727756796859966450198 + 891054669958697657727756796750957550198 step 65: 1782110429016395315455513593610924000396 + 6930004290163953155545135936109240112871 step 66: 8712114719180348471000649529720164113267 + 7623114610279259460001748430819174112178 step 67: 16335229329459607931002397960539338225445 + 54452283393506979320013970695492392253361 step 68: 70787512722966587251016368656031730478806 + 60887403713065686361015278566922721578707 step 69: 131674916436032273612031647222954452057513 + 315750254459222746130216372230634619476131 step 70: 447425170895255019742248019453589071533644 + 446335170985354910842247910552598071524744 step 71: 893760341880609930584495930006187143058388 + 883850341781600039594485039906088143067398 step 72: 1777610683662209970178980969912275286125786 + 6875216825722199690898710799022663860167771 step 73: 8652827509384409661077691768934939146293557 + 7553926419394398671967701669044839057282568 step 74: 16206753928778808333045393437979778203576125 + 52167530287797973439354033380887782935760261 step 75: 68374284216576781772399426818867561139336386 + 68363393116576881862499327718767561248247386 step 76: 136737677333153663634898754537635122387583772 + 277385783221536735457898436366351333776737631 step 77: 414123460554690399092797190903986456164321403 + 304123461654689309091797290993096455064321414 step 78: 718246922209379708184594481897082911228642817 + 718246822119280798184495481807973902229642817 step 79: 1436493744328660506369089963705056813458285634 + 4365828543186505073699809636050668234473946341 step 80: 5802322287515165580068899599755725047932231975 + 5791322397405275579959988600855615157822232085 step 81: 11593644684920441160028888200611340205754464060 + 06046445750204311600288882006114402948644639511 step 82: 17640090435124752760317770206725743154399103571 + 17530199345134752760207771306725742153409004671 step 83: 35170289780259505520525541513451485307808108242 + 24280180870358415431514552502550595208798207153 step 84: 59450470650617920952040094016002080516606315395 + 59351360661508020061049004025902971605607405495 step 85: 118801831312125941013089098041905052122213720890 + 098027312221250509140890980310149521213138108811 step 86: 216829143533376450153980078352054573335351829701 + 107928153533375450253870089351054673335341928612 step 87: 324757297066751900407850167703109246670693758313 + 313857396076642901307761058704009157660792757423 step 88: 638614693143394801715611226407118404331486515736 + 637515684133404811704622116517108493341396416836 step 89: 1276130377276799613420233342924226897672882932572 + 2752392882767986224292433320243169976727730316721 step 90: 4028523260044785837712666663167396874400613249293 + 3929423160044786937613666662177385874400623258204 step 91: 7957946420089572775326333325344782748801236507497 + 7947056321088472874435233336235772759800246497597 step 92: 15905002741178045649761566661580555508601483005094 + 49050038410680555508516666516794654087114720050951 step 93: 64955041151858601158278233178375209595716203056045 + 54065030261759590257387133287285110685815114055946 step 94: 119020071413618191415665366465660320281531317111991 + 199111713135182023066564663566514191816314170020911 step 95: 318131784548800214482230030032174512097845487132902 + 209231784548790215471230030032284412008845487131813 step 96: 527363569097590429953460060064458924106690974264715 + 517462479096601429854460060064359924095790965363725 step 97: 1044826048194191859807920120128818848202481939628440 + 0448269391842028488188210210297089581914918406284401 step 98: 1493095440036220347996130330425908430117400345912841 + 1482195430047110348095240330316997430226300445903941 step 99: 2975290870083330696091370660742905860343700791816782 + 2876181970073430685092470660731906960333800780925792 step 100: 5851472840156761381183841321474812820677501572742574 + 4752472751057760282184741231483811831676510482741585 step 101: 10603945591214521663368582552958624652354012055484159 + 95148455021045325642685925528586336612541219554930601 step 102: 105752400612259847306054508081544961264895231610414760 + 067414016132598462169445180805450603748952216004257501 step 103: 173166416744858309475499688886995565013847447614672261 + 162276416744748310565599688886994574903858447614661371 step 104: 335442833489606620041099377773990139917705895229333632 + 236333922598507719931099377773990140026606984338244533 step 105: 571776756088114339972198755547980279944312879567578165 + 561875765978213449972089745557891279933411880657677175 step 106: 1133652522066327789944288501105871559877724760225255340 + 0435525220674277789551785011058824499877236602252563311 step 107: 1569177742740605579496073512164696059754961362477818651 + 1568187742631694579506964612153706949755060472477719651 step 108: 3137365485372300159003038124318403009510021834955538302 + 2038355594381200159003048134218303009510032735845637313 step 109: 5175721079753500318006086258536706019020054570801175615 + 5165711080754500209106076358526806008130053579701275715 step 110: 10341432160508000527112162617063512027150108150502451330 + 03315420505180105172021536071626121172500080506123414301 step 111: 13656852665688105699133698688689633199650188656625865631 10018999583 takes 111 iterations / steps to resolve into a 56 digit palindrome. REVERSAL-ADDITION PALINDROME RECORDS Most Delayed Palindromic Number for each digit length (Only iteration counts for which no smaller records exist are considered. My program records only the smallest number that resolves for each distinct iteration count. For example, there are 18-digit numbers that resolve in 232 iterations, higher than the 228 iteration record shown for 18-digit numbers, but they were not recorded, as a smaller [17-digit] number already holds the record for 232 iterations.) Digits Number Result 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 89 187 1,297 10,911 150,296 9,008,299 10,309,988 140,669,390 1,005,499,526 10,087,799,570 100,001,987,765 1,600,005,969,190 14,104,229,999,995 100,120,849,299,260 1,030,020,097,997,900 10,442,000,392,399,960 170,500,000,303,619,996 1,186,060,307,891,929,990 solves in 24 iterations. solves in 23 iterations. solves in 21 iterations. solves in 55 iterations. solves in 64 iterations. solves in 96 iterations. solves in 95 iterations. solves in 98 iterations. solves in 109 iterations. solves in 149 iterations. solves in 143 iterations. solves in 188 iterations. solves in 182 iterations. solves in 201 iterations. solves in 197 iterations. solves in 236 iterations. solves in 228 iterations. solves in 261 iterations - World Record! [View all records] This reverse and add program was created by Jason Doucette. Please visit my Palindromes and World Records page. You have permission to use the data from this webpage (with due credit). A link to my website is much appreciated. Thank you. (This program has been run 2,549,994 times since Saturday, March 9th, 2002.)