"friendly numbers"/"amicable numbers"

friendly numbers are

pairs of

numbers such that each number is the

sum of the

divisors of the other number.

the "

pythagoreans" made the extraordinary discovery that 220 and 284
are friendly numbers.

the divisors of 220 are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55, 110, and the sum of
all these is 284.

on the other hand the divisors of 284 are 1, 2, 4, 71, 142, and the sum of these
is 220.

the pair is said to be

symbolic of

friendship.

Martin Gardners book "

mathematical magic show" tells of

talismans sold
in the

middle ages which were inscribed with these numbers on the grounds that
wearing the

charms would

promote love.

an arab

numerologist documents the practice of carving 220 on one fruit and 284
on another, and then eating the first one and offering the second one to a lover
as a form of mathematical

aphrodisiac.

*taken from "fermats last theorem" by Simon Singh*
so now you know what to do if quoting pi to 100 decimals fails to allure the
object of your affections.