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 $237$.

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