13. (6 points) $a, b, c$ are three distinct natural numbers, and $a+b+c=48$, then the maximum product of $a, b, c$ is
【Solution】Solution: $48 \div 3=16$,
$$
\begin{array}{l}
16-1=15, \\
16+1=17,
\end{array}
$$

Therefore, the maximum product of $a, b, c$ is: $15 \times 16 \times 17=4080$. The answer is: 4080.