A very special number

$\text{A perfect number is a positive integer that is equal to the sum of its proper positive divisors}$

6 is a perfect number. Because $1 + 2 + 3 =6$

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

Now add the factors,

$1+2+4+7+ 14 = \boxed{28}.$

All perfect numbers found so far can be represented as $(2^{n-1})(2^n-1)$ where $2^n-1$ is prime.
6= $(2^{2-1})(2^2-1)$ . $2^2-1$ is prime when n=2. $2^n-1$ is laso prime when n=3 as $2^3-1=7$ .
$(2^{3-1})(2^3-1)$ =4(7)= 28