Algorithm to check if a number if a perfect number

Question

I am looking for an algorithm to find if a given number is a perfect number.

The most simple that comes to my mind is :

1. Find all the factors of the nu

Answer 1

Here's a quick algorithm just for fun, in PHP - using just a simple for loop. You can easliy port that to other languages:

function isPerfectNumber($num) {
        $out = false;

        if($num%2 == 0) {
            $divisors = array(1);
            for($i=2; $i<$num; $i++) {
                if($num%$i == 0)
                    $divisors[] = $i;
            }

            if(array_sum($divisors) == $num)
                $out = true;
        }

        return $out ? 'It\'s perfect!' : 'Not a perfect number.';
    }

Hope this helps, not sure if this is what you're looking for.