Perfect number - Wikipedia

In number theory, a perfect number is a positive integer that is equal to the sum of its positive ... He also said (wrongly) that the perfect numbers end in 6 or 8 alternately. ... p = 2, 3, 5, 7, 13, 17, 19, 31, 61, 89, 107, 127, 521, 607, 1279, 2203, 2281, 3217, 4253, 4423, 9689, 9941, 11213, 19937, 21701, 23209, 44497, 86243, ...