vampire number
Consider the integer 1395. In the equation
expressed in base 10, both sides (http://planetmath.org/Equation) use the same digits.
When a number with an even number
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 number. 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 |