Explanation:
We can factor out 8 like so
2^40 + 2^39 + 2^36 = 2^3*2^37 + 2^3*2^36 + 2^3*2^33
2^40 + 2^39 + 2^36 = 2^3*(2^37 + 2^36 + 2^33)
2^40 + 2^39 + 2^36 = 8*(2^37 + 2^36 + 2^33)
Showing that 8 is a factor of 2^40 + 2^39 + 2^36
In other words, 2^40 + 2^39 + 2^36 is divisible by 8
