Sum of the digits of $N=5^{2012}$ The sum of the digits of $N=5^{2012}$ is computed.
The sum of the digits of the resulting sum is then computed.
The process of computing the sum is repeated until a single digit number is obtained.
What is this single digit number?

Hint: if $s$ is the sum of digits of a number $a$ then
$$s\equiv a\pmod 9.$$
Now all you need too do is compute $5^{2012} \pmod 9$.
