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

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