Whole number for which the sum of its proper divisors is greater than the number itself.

All whole numbers can be classified in one of these three classes:

- Abundant numbers,
- Perfect numbers,
- Deficient numbers.

### Examples

- Consider the whole number 20.

The sum of its proper divisors is 22, like this: 1 + 2 + 4 + 5 + 10 = 22.

Because 22 > 20, this means that 20 is an*abundant number*. - Consider the number 81.

The sum of its proper divisors is 40: 1 + 3 + 9 + 27 = 40.

Because 40 < 81, this means that 81 is not an abundant number.