Question

What is the greatest factor of 63 that is also a prime number?
7
9
13
21

Answer 1

The answer is either 9 or 7

Answer 2

7

Explanation:

Note the factors of each number. Prime numbers are numbers that can only be factored to itself and 1. Note:

Factors of 1:

1

Factors of 3:

1 , 3

Factors of 7:

1 , 7

Factors of 9:

1 , 3 , 9

Factors of 21:

1 , 3 , 7 , 21

Factors of 63:

1 , 3 , 7 , 9 , 21 , 63