A Pre-RMO question! -3

Let $\overline{abc}$ be a three-digit numbers with non-zero digits such that $a^2+b^2=c^2$ . What is the largest possible prime factor of $\overline{abc}$ ?

Note : $a$ , $b$ , and $c$ are digits of $\overline{abc}$ just like $2$ , $3$ , and $7$ are digits of $237$ .