What are the the prime factors of 84

Start with the lowest prime number: 2

is 84 divisible by 2? Yes

so. 84/2 = 42

Check if it still divisible by 2,
yes, 42/2 =  21

check if it is still divisible by 2,
no, move to next prime number = 3.

check if it is divisible by 3
yes, 21/3 = 7.

now since, 7 is a prime number, we stop.

and the prime factors of 84 are : 2,2, 3, 7
4 prime factors, 3 distinct.