A pair of numbers, each of which is the sum of the factors of the other (e.g. 220 and 284).
Example sentencesExamples
One particular interest involved what we now call amicable numbers.
The Pythagoreans were also interested in what we now call amicable numbers - pairs in which each number is the sum of the proper divisors of the other.
Today, the tally of known amicable numbers has grown to about two and half million.