the vampire numbers that have at most 10 digits. Multiple fang pairs A vampire number can have multiple distinct pairs of fangs. The first of infinitely many vampire numbers with 2 pairs of fangs: 125460 = 204 × 615 = 246 × 510 The first with 3 pairs of fangs: 13078260 = 1620 × 8073 = 1863 × 7020 = 2070 × 6318 The first with 4 pairs of fangs: 16758243290880 = 1982736 × 8452080 = 2123856 × 7890480 = 2751840 × 6089832 = 2817360 × 5948208 The first with 5 pairs of fangs: 24959017348650 = 2947050 × 8469153 = 2949705 × 8461530 = 4125870 × 6049395 = 4129587 × 6043950 = 4230765 × 5899410 Variants Pseudovampire numbers (disfigurate vampire numbers) are similar to vampire numbers, except that the fangs of an n-digit pseudovampire number need not be of length n/2 digits. Pseudovampire numbers can have an odd number of digits, for example 126 = 6 × 21. More generally, more than two fangs are allowed. In this case, vampire numbers are numbers n which can be factorized using the digits of n. For example, 1395 = 5 × 9 × 31. This sequence starts : 126, 153, 688, 1206, 1255, 1260, 1395, ... A vampire prime or prime vampire number, as defined by Carlos Rivera in 2002, is a true vampire number whose fangs are its prime factors. The first few vampire primes are: 117067, 124483, 146137, 371893, 536539 the largest known is the square (94892254795 × 10103294 + 1)2, found by Jens K. Andersen in September, 2007. A double vampire number is a vampire number which has fangs that are also vampire numbers, an example of such a number is 1047527295416280 = 25198740 × 41570622 = (2940 × 8571) × (5601 × 7422) which is the smallest double vampire number. A Roman numeral vampire number is vampire number that uses Roman numerals instead of base-10. An example of this number is II × IV = VIII. References External links Sweigart, Al. Vampire Numbers Visualized Base-dependent integer sequences