Definition:Reversal

Definition
Let $m = \left[{a_n a_{n-1} a_{n-2} \ldots a_2 a_1 a_0}\right]$ be an integer expressed in base $10$.

That is:
 * $m = \displaystyle \sum_{k \mathop = 0}^n a_k 10^k$

Its reversal $m'$ is the integer created by writing the digits of $m$ in the opposite order:
 * $m' = \left[{a_0 a_1 a_2 \ldots a_{n-2} a_{n-1} a_n}\right]$

That is:
 * $m' = \displaystyle \sum_{k \mathop = 0}^n a_{n - k} 10^k$