Answer
$20 = 2\cdot 2\cdot 5$
Work Step by Step
The $\textit{prime factorization}$ of a number is obtained by writing the number as a product of primes.
To determine the prime factorization of $20$ we write the number as a product of factors and continue the process until all factors are prime numbers.
We start by writing $20$ as a product of two numbers:
$20=2\cdot 10$.
The number $2$ is prime, but $10$ is not. So we write $10=2\cdot 5$:
$20=2\cdot 2\cdot 5$.
Now each factor is a prime number, therefore the prime factorization of $20$ is $2\cdot 2\cdot 5$.