# How do you write the prime factorization of 81?

$3 \times 3 \times 3 \times 3$

#### Explanation:

Prime factorization is where we take a number, such as 81, and break it down into its prime factors.

For instance, $9 \times 9 = 81$.

9 is a factor of 81. But 9 isn't prime. $3 \times 3 = 9$. 3 is prime.

And so we can use that to rewrite what we started with:

$9 \times 9 = \textcolor{red}{3 \times 3 \times 3 \times 3} = 81$

The red is the prime factorization.