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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: ( You must be logged in to post comments.)
  Subject Author Date
Solution (for no mandated format)Dej Mar2012-11-01 01:31:13
Solutioncomputer solutionCharlie2012-10-31 12:45:40
Year in vampire number or fang?Jer2012-10-31 12:28:28
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