2. (5 points) There are 15 numbers, their average is 17, after adding 1 number, the average becomes 20, then the added number is . $\qquad$
【Analysis】First, according to the problem, we can get: the sum of the original 15 numbers is $255(15 \times 17=255)$, and the sum of the later 16 numbers is $320(16 \times 20=320)$; then, by subtracting the sum of the original 15 numbers from the sum of the later 16 numbers, we can find out what the added number is.

【Solution】Solution: $16 \times 20-15 \times 17$
$$
\begin{array}{l}
=320-255 \\
=65
\end{array}
$$

Answer: The added number is 65.
Therefore, the answer is: 65.