The proper divisors of 12 are 1, 2, 3, 4 and 6. A proper divisor of an integer N is a positive divisor of N that is less than N. What is the sum of the proper divisors of the sum of the proper divisors of 280?

Guest May 22, 2021

#1**+1 **

Simple calculations get 640 (Just list out all of the factors and add! )

ilovepizza547 May 22, 2021