To find out what number is 25% of 64, we can set up the equation using the concept of percentages.
Let \( x \) be the number we are trying to find. We express 25% as a decimal, which is \( 0.25 \).
We can write the equation as:
\[ x = 0.25 \times 64 \]
Now, we can solve for \( x \):
\[ x = 0.25 \times 64 = 16 \]
Thus, the number that is 25% of 64 is \( \boxed{16} \).