Question

Which number has only two factors: 21, 23, 25, 27?

Answer 1

Here is the answer:-

Explanation:

Out of all the numbers that you have written, 21,23, 25 and 27,

only 23 is a prime number and this it is the only number in the series which has 2 factors.
i.e. 1 and 23.

Answer 2

23, because it is the only prime number on this list, and therefore only has two factors, the numbers 1 and 23.

Explanation:

When you multiply two numbers together, those two numbers are the factors of the product or your answer. For the number 21, you can multiply 1 and 21 together or 3 and 7 together to get the number 21, so it has four factors, 1, 3, 7, 21.

For the number 25, you can multiply 1 and 25 together or 5 and 5 to get 25, so it has three factors, 1, 5, 25.

For the number 27, you can multiply 1 and 27 together or 3 and 9 to get 27, so it has four factors, 1, 3, 9, 27.

For the number 23, only two whole numbers multiply together to get this number is 1 and 23, so those are its only two factors, 1 and 23.