Just what is a Vampire Number?

It's two numbers of equal length multiplied with the result having every digit occuring in both factors.
That sounds like somethin' a dummy would write, so these first seven vampires explain it all.

21 x 60 = 1260
15 x 93 = 1395
35 x 41 = 1435
30 x 51 = 1530
21 x 87 = 1827
27 x 81 = 2187
80 x 86 = 6880

Numbers like 350 x 410 and 3500 x 4100 don't count for obvious reasons. Even dummies can figure this one out.

If you're not a dummy and want to see just how far this insanity has gone, check out the current
World Record holder's web site or go to Wikipedia's Page.

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If you want to see how insane I am,. . . read on.
( No mathemeticians or Jens K. Andersen allowed. )

This Section For Dummies Only.

    This all started from a "Brain Bogglers" article by Clifford Pickover in
Discover magazine back in '95.  The largest number he stated in that article was 20 digits long.

1234554321 x 9162361086 = 11311432469283552606

Clifford Pickover's RealityCarnival

Since I was attempting to teach myself how to progam in C,  I came up with a
program that could find a "massive" 24 digit number!   My record with this program was:

999999456323 x 999999718613 = 999999174936152983639999

I sent my "massive" number to Clifford only to be dumbfounded to learn that
John Childs had found an "amazingly massive" 40 digit number:
98765432198765432198 x 98765432198830604534 = 9754610597415368368844499268390128385732

I wasn't going to be outdone.  Since I could only squeeze 15 digit accuracy out of my original program,
I went back to elementary school and wrote a program to multiply numbers just like a 3rd grader would.
I doubled that number and realized what a worthless endeavor this was.  I gave up on this 80 digit number in '96.

9999999876543219876543219876543219876543 x 9876543219876543219876543210000011652393 =
98765430979439207522649183967093846153556319442527268359317291816109486890517399

Fast forward six years.  I type "Vampire Numbers" into google and realized that this worthless endeavor
was still ongoing.  Now there's a 100 digit record found by Myles Hilliard on March 9 1999.  This may be the number:

98765432109876543210987654321098765432108990776898 x 98765432109876543210987654321098765432109967196255 =
9754610579850632525872580399376009754616397617223948488986906097184011734546933285857249127286116990

I wasn't going to be outdone, . . again!.  A simple program update and more numbers appeared.

110 digit
2445678901234567890123456789012345678901234567890178388 x
5189012345678901234567890123456789012345678901234567890 =
1269065801207258294799601000947847617241573513438864730
3583557468366887859319541997180239520842852484196761320

120 digit
723456789012345678901234567890123456789012345678901236502487 x
866789012345678901234567890123456789012345678901234567890123 =
627084395622787314733746618990521450650766823940248151958428
947255718933046696721836782155036889463789010071207432235901

130 digit
32350984609022690782893943984866261193744563228898793785074827285 x
90477302018811435996802350976680592791782792174511586750062603890 =
29270298050764663952226800797615648838524062777378099849839992125
40387327808520902634152487931663808554006321894797981879119138650

140 digit
3254321098765432109876543210987654321098765432109876543210987655234357 x
8732109876543210987654321098765432109876543210987654321098765432109876 =
2841708940797258411226514592837330334455200920962666880847981367757436
5527956852714908168124702065097791331338311245616684335809953754209732

150 digit
133456789012345678901234567890123456789012345678901234567890123456789338245 x
926789012345678901234567890123456789012345678901234567890123456789012345678 =
123686285679577503739425637891089352540823614129253829300442529718796269690
544417613473924614558640746776988903209811373174192385602740363388805855110

160 digit
31234567890123456789012345678901234567890123456789012345678901234567890125684601 x
43210987654321098765432109876543210987654321098765432109876543210987654321098765 =
13496765274881789010341390149319460139760478126458901023894175423514246075426566
88863678045354255321682214283882900303559757917873122580539026936929074160617765

170 digit
4289012345678901234567890123456789012345678901234567890123456789012345678901234655970 x
6201234567890123456789012345678901234567890123456789012345678901234567890123456789012 =
2659717162013150591372782946654425083417157187216887186609205865449672301223842456210
5210107237533493576964597643017584592833870942136598342498980959078430208390696201640

180 digit
317654321098765432109876543210987654321098765432109876543210987654321098765432109876725511 x
428901234567890123456789012345678901234567890123456789012345678901234567890123456789012345 =
136242330485085481333829672961915079779044719226189793047447511417227604352971045756500121
592455568696034308584282306029896118120136400563728318931544299780671576766818872355433295


This is about the time (Nov. '02) I discovered Jens' 10060 digit number.
You just had to go and spoil the fun for us dummies didn't ya. There's no
formulas, mod9 congruences, special number sequences or anything but a shot
in the dark to find these vampires. Since you jumped from 100 to 10060 digits,
I awarded myself the"Record Vampire Number for Dummies" with this gold star I
proudly wear on my forehead.

What? . . Me Worry!    I'm not gonna be intimidated like every one else.   The hunt continues . . . .
( . . over six years later when this website was created ( 7-09 ) and just needed some filler material. )



190 digit (found 7-28-09)
31567890123456789012345678901234567890123456789012345678901234567890123456789012345678907527710 x
43109876543210987654321098765432109876543210987654321098765432109876543210987654321098765432109 =
13608878459518716378064354491017683734422893201974401803050651428590386267687570739251612998138
96390004538485789205563257795727793667089926155460707294421242197329641366521715851331041240390

200 digit (found 7-29-09)
3154321098765432109876543210987654321098765432109876543210987654321098765432109876543210987656787176 x
4389012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345 =
1384435424471691827768294011308941883984105436683731668496905279332543739181539695042982501617863467
5015707621780322476856907419153578259062146577620893532933557240810502512832764930158447960901687720

210 digit (found 8-7-09)
260987654321098765432109876543210987654321098765432109876543210987654321098765432109876543210987661716352 x
813456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345 =
212302179255905046457702987498981547035219279532054040436058615291891182654017650377884618249036753161747
276186633731765452124891224087660590296283205818380035260713174993958834646184635179297338689397616365440

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Click HERE for in between numbers.
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LATEST NUMBER

420 digit (found 1-09-13)
821789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678
901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234568557405 x
874501234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012504 =

718655505850623297373814044416256575909513174737740069188452882090313175726178106324332489507604716838277
618472579476526133119120500829058838834620562758633524163380499205089764599384147927825931939571345492304
649544095039637262715212011592646029691377085822348956867556020515287714534381982701723519395000884051982
941616446579482769486480389431501250191435446143972076726880060883936291409518457673064328620517786792120



If you have a bigger number and your name isn't Jens K. Andersen ,
I hearby allow you to print this "Silver Star" award and stick on your forehead
if the sum of both of your factor digits is a modulus 9 congruence.




You can still reclaim the "Gold Star Award" by sending a number with factors that don't
have any modulus 9 congruence. (  NO!   Jens.   You still can't play. )