What is the sum of all the factors of 36?

Explanation

1. 01

   $36 = 2^2 \times 3^2$.

2. 02

   Sum of factors = $(1 + 2 + 4)(1 + 3 + 9) = 7 \times 13 = 91$.

3. 03

   Check: $1 + 2 + 3 + 4 + 6 + 9 + 12 + 18 + 36 = 91$.