Japanese coins, a plastic bag

2001

photo by Takagi Shigeki

cf. 220 and 284 are the amicable pair which Pythagoras et al. found in about 500 B. C.

(Two numbers are called amicable if each equals to the sum of the divisors of the other.)

Divisors of 220: 1 + 2 + 4 + 5 + 10 + 11 + 20 + 22 + 44 + 55 + 110 = 284

Divisors of 284: 1 + 2 + 4 + 71 + 142 = 220