Amicable numbers

Amicable numbers are two different numbers where the sum of the proper divisors of one of the numbers is equal to the other. (A proper divisor is a positive integer other than the number itself.) For example, the proper divisors of 220 are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 & 110, which total 284; the proper divisors of 284 are 1, 2, 4, 71, & 142, which total 220.