# Perfect Numbers

A perfect number is a number that is equal to the sum of all its factors other than itself.

For example, the factors of $6$ are $1,2,3$ , and $6$ . Since

$1+2+3=6$ ,

$6$ is a perfect number.

The next perfect number is $28$ . The factors of $28$ are $1,2,4,7,14$ , and $28$ , and

$1+2+4+7+14=28$ .