Add a function for prime perfect number

[sylhare]

Given a positive integer
When passed to the function it will tell if it is a perfect number or not

In number theory, a perfect number is a positive integer that is equal to the sum of its proper positive divisors, that is, the sum of its positive divisors excluding the number itself:

# divisor of 6
6 = 1 x 6
6 = 2 x 3
6 = 3 x 2

# Sum of divisor
6 = 1 + 2 + 3

Source:
https://en.wikipedia.org/wiki/Perfect_number