amicable number
noun
mathematics
: either of a pair of numbers each of which equals the sum of the different exact divisors of the other excluding the number itself
Note: 220 and 284 are examples of amicable numbers. The factors of 220 are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55, and 110, which sum to 284, while the factors of 284 are 1, 2, 4, 71, and 142, which sum to 220.
Word History
First Known Use
circa 1763, in the meaning defined above