Perfect Number:

Find a number say 6. The factors of 6 are 1, 2 and 3.

When you add factors 1,2, and 3 we get 1+2+3 = 6. Hence 6 is a perfect number

Say another number 28. The factors of 28 are

2 | 28

2  | 14

 7  | 7 

    | 1

So factors are 1,2, 4, 7, and 14

Now lets add 1+2+4+7+14 = 28 Hence 28 is a perfect number