Vampire Numbers

If you thought that vampires have absolutely nothing do with maths, well a small girl from Romania (the land of Dracula) will tell you otherwise. The definition is not that hard to understand:

In mathematics, a vampire number (or true vampire number) is a composite natural number v, with an even number of digits n, that can be factored into two integers x and y each with n/2 digits and not both with trailing zeroes, where v contains precisely all the digits from x and from y, in any order, counting multiplicity. x and y are called the fangs.

To make this more clear think of the example 1260 = 21 x 60 (which is on the back). 1260 has an even number of digits (4) and it can be factored (written as a product) of 2 numbers, 21 and 60, which have 4/2 = 2 digits. Also 21 and 60 use the exact digits that appear in 1260, which are 1, 2, 6 and 0. Quite interesting, don't you think?

I have created this designs to make people more excited about number facts and mathematics in general.

More info: teespring.com