# Amicable Numbers

Two numbers are said to be amicable if each is equal to the sum of the proper divisors of the other.

### Historical Notes

**~850AD***Thabit ibn Qurra writes Book on the determination of amicable numbers which contains general methods to construct amicable numbers. He knows the pair of amicable numbers 17296, 18416.***1636***Fermat discovers the pair of amicable numbers 17296, 18416 which were known to Thabit ibn Qurra 800 years earlier.*

**See also: **Divisor.

**Subjects: ** Mathematics