# 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 206

- 206 is the number of bones in a normal human skeleton
- 206 is the smallest number whose English name contains all five vowels exactly once (twO hUndrEd And sIx)
- 206 is the smallest number n such that n and n+1 have the same sum of divisors but an unequal number of divisors

## Common Properties of 206

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.

A number is *even* if it is divisible by 2.

Numbers that are not even are odd. 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 number is said to be *square-free* if its prime decomposition contains no repeated factors.

The next *Ulam* number is uniquely the sum of two earlier distinct Ulam numbers.

The *untouchable* numbers are those that are not the sum of the proper divisors of any number.