To find the median, first arrange the numbers in increasing order:
\[
6, 8, 9, 13, 15, 16, 18, 20, 21, 22, 25.
\]
Since there are 11 numbers, the median is the middle number, which is the 6th term in the ordered list:
\[
\text{Median} = 16.
\]
Thus, the correct answer is \( \boxed{16} \).