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Vampire numbers (Posted on 2012-10-31) Difficulty: 3 of 5
A "vampire number" is an integer with 2n digits that is the product of two n-digit numbers the fangs whose digits, when combined, form a permutation of the original digits (thus, multiplicity counts).

The smallest vampire numbers are 1260 (= 21 60) and 1395 (= 15 93). Technical point: The fangs cannot each end in a 0. So 126000 is not a vampire number.

You might have missed it, but October 5, 2010, was a vampire day because 10 05 2010 is an 8-digit vampire number. It equals 2010 5001. When is the next vampire day?

No Solution Yet Submitted by Danish Ahmed Khan    
Rating: 5.0000 (2 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Year in vampire number or fang? | Comment 1 of 3

It doesn't fit your example but 2012 x 5021 = 10102252 is the first of 3 vampire numbers with 2012 in a fang.  The other fang could be interpreted as May 21. 

More similar to your example but with YYYYMMDD format is
4091 x 5021 = 20540911
Which is September 11, 2054

The next date fitting precisely to your example is
1502 x 8024 = 12052048
December 5, 2048

Finally in honor of Halloween we had
1101 x 9366 = 10311966
which is the birthdate of Ad Rock from the Beastie Boys.

  Posted by Jer on 2012-10-31 12:28:28
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