You know what they are amicable numbers?
Figures friendly pairs of numbers are where one is the sum of the splitters of the other. For example, the dividers 220 are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110, the sum is 284. Moreover, the dividers 284 are 1, 2, 4, 71 and 142 and their sum is 220. Fermat also discovered the pair 17,296 and 18,416. Descartes discovered the pair 9,363,584 and 9,437,056.
