Euler in Babylon

Sum of squares of unitary divisors

May 26, 2013

A unitary divisor d of a number n is a divisor of n that has the property gcd(d, n/d) = 1. The unitary divisors of 4! = 24 are 1, 3, 8 and 24. The sum of their squares is 12 + 32 + 82 + 242 = 650.

Let S(n) represent the sum of the squares of the unitary divisors of n. Thus S(4!)=650.

Find S(100 000 000!) modulo 1 000 000 009.


gamwe6

Written by gamwe6 who lives and works in San Francisco building useful things. You should follow him on Twitter