A vampire number is a number with an even number of digits that, when split into a pair of numbers with an equal number of digits (x and y) and multiplied, results in the original number (v). In the above expression, x and y are the fangs. A single vampire number may have more than one pair of fangs, as you can put its digits in any order you like.
1260 has only one pair: 21 x 60
125,460 has two pairs: 204 x 615 and 246 x 510.
24,959,017,348,650 has five pairs of fangs and likes to spend its weekends lurking in dark alleys and the woods bordering lonely rest areas: 2947050 x 8469153, 2949705 x 8461530, 4125870 x 6049395, 4129587 x 6043950 and 4230765 x 5899410.
A true vampire number has only two fangs, neither of which end in zero. Variants include vampire numbers with more than two fangs, and pseudovampire numbers, which have fangs comprised of numbers with an odd number of digits.