vampire number

Consider the integer 1395. In the equation


expressed in base 10, both sides ( use the same digits.

When a number with an even numberMathworldPlanetmath of digits is also the product of two multiplicands having half as many digits as the product, and together having the same digits, the product is called a vampire number. The multiplicands are called fangs.

By definition, a vampire number can’t be a prime numberMathworldPlanetmath. But if both of its fangs are prime numbers, then it might be referred to as a “prime vampire number.”

This concept can be applied to any positional base, and to Roman numerals. For example,


A vampire number is automatically a Friedman number also.

Title vampire number
Canonical name VampireNumber
Date of creation 2013-03-22 15:45:10
Last modified on 2013-03-22 15:45:10
Owner CompositeFan (12809)
Last modified by CompositeFan (12809)
Numerical id 8
Author CompositeFan (12809)
Entry type Definition
Classification msc 11A63
Defines vampire number
Defines fang