Answer
$2^{2}\times5$
Work Step by Step
In order to find the prime factorization of 20, we can try to divide 20 by the first prime, 2.
$20\div2=10$
Try to divide 10 by 2.
$10\div2=5$
5 itself is a prime number, so we cannot simplify any more. The prime factorization of 20 is $2\times2\times5=2^{2}\times5$.