# 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 567

- 567 is the smallest possible sum of primes which are formed using all ten digits: 401 + 89 + 67 + 5 + 3 + 2 = 567 (submitted by David Bernstein)
- 567 is the smallest number that together with its square uses the digits 1-9 exactly once

## Common Properties of 567

A positive integer greater than 1 that is not prime is called *composite*.

Composite numbers are opposite to prime numbers.

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.

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

Guess what odious numbers are.

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.