The difference of two squares is given by the identity:
\[ a^2 - b^2 = (a - b)(a + b) \]
In the case of \(81 - 16\), we can rewrite this expression using squares. Notice that:
\[ 81 = 9^2 \quad \text{and} \quad 16 = 4^2 \]
Thus, we can write:
\[ 81 - 16 = 9^2 - 4^2 \]
Now, applying the difference of squares identity:
\[ 9^2 - 4^2 = (9 - 4)(9 + 4) \]
Calculating the individual terms gives us:
\[ 9 - 4 = 5 \quad \text{and} \quad 9 + 4 = 13 \]
Therefore, we have:
\[ 81 - 16 = (9 - 4)(9 + 4) = 5 \times 13 \]
Thus, the product equal to \(81 - 16\) is:
\[ 5 \times 13 \]