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!

Because $a^p \equiv a \pmod p$ (where $p$ is a prime) by Fermat's little theorem. (Think $3^7$ as $a$.)
