To prove the divisibility lets expand each number first to get the complete picture of the problem
51^7 = 8.974106779 . 10^11
51^6 = 1.75962878 . 10^10
(51^7 - 51^6) = 8.974106779 . 10^11 - 1.75962878 . 10^10
= 8.798143901. 10^11
= 3.51925756. 10^10
That is the answer expressed in scientific notation
= 35192575600
Which means the divisibility is proven