The difference of highest common factor to the second highest common factor of 64 and 32 is
Factor of 64 = 1, 2, 4, 8, 16, 32 and 64
Factor of 32 = 1, 2, 4, 8, 16, and 32
Common Factor = 1, 2, 4, 8, 16, and 32
Difference between highest and lowest common factor = 32 - 16 = 16
So the answer is 16.