+486 What is the sum of the final three digits of the integer representation of $5^{100}$?
+486 Nevermind, I got the answer, it is $13$, because for $5^n$, starting with $n=3$, we have the final digits as $125,625,125,625,125,625...$ and so on. Since $100$ is a multiple of $2$, it ends in $625$, and the sum of the digits is $\boxed{13}$
