# 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 1071

- 1071 is the smallest composite number ending in 1, 3, 7 or 9 that yields no primes if its first digit is changed to another non-zero digit (1071, 2071, 3071, 4071, 5071, 6071, 7071, 8071 and 9071 are all composite numbers)

## Common Properties of 1071

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.