# Number Gossip

(Enter a number and I'll tell you everything you wanted to know about it but were afraid to ask.)

## Unique Properties of 251

- 251 is the smallest prime which is an anagram is a cube (actually it is an anagram of two cubes: 125 and 512
- 251 is the smallest prime with digital product equal to ten
- 251 is the smallest number that can be written as the sum of 3 positive cubes in 2 ways: 251 = 2
^{3} + 3^{3} + 6^{3} = 1^{3} + 5^{3} + 5^{3}

## Common Properties of 251

The number n is called an *apocalyptic power* if 2^{n} contains the consecutive digits 666 (in decimal).

The number n is *deficient* if the sum of all its positive divisors except itself is less than n.

Compare with perfect and abundant numbers.

A number is *odd* if it is not divisible by 2.

Numbers that are not odd are even. Compare with another pair -- evil and odious numbers.

The number n is *odious* if it has an odd number of 1's in its binary expansion.

Guess what evil numbers are.

A *prime* is a positive integer greater than 1 that is divisible by no positive integers other than 1 and itself.

Prime numbers are opposite to composite numbers.

A number is said to be *square-free* if its prime decomposition contains no repeated factors.