3 If the three-digit decimal number $n=\overline{a b c}$ satisfies that $a$, $b$, and $c$ form an arithmetic sequence, then the maximum possible prime factor of $n$ is $\qquad$
(3) 317 Hint: $3 \mid n, 999=27 \cdot 37, 987=3 \cdot 7 \cdot 47, 963=$ $27 \cdot 103, 951=3 \cdot 317$.