Fermats Little Theorem: How $(3^7)^{17}$ will leave the same remainder when divided by $17$ as $3^7$? As it is used in this explanation, how and why $(3^7)^{17}$ will leave the same remainder when divided by $17$ as $3^7$?
Thanks!

Fermat's little theorem says  that 
$$a^p = a \mod p$$
for prime p.
Here $a$ is $3^7$ and prime $p$ is $17$. If you need to prove FLT, there is a wikipedia article on just that subject.
