What is the sum of the factors of 21?

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To answer this question, we first need to work out the factors of 21. These are the whole numbers which multiply to make 21. 

We know that 1 multiplies with 21 to make 21, so they are both factors. 

2 is not a factor of 21, because we cannot multiply it with another whole number to make 21.

3 is a factor of 21, because it multiplies with 7 to make 21. 

Therefore the factors of 21 are 1, 3, 7 and 21. 

All that is left to do is to work out the sum of these numbers, that is to add them all up. 

21+1 + 3 +7 = 32

Therefore, the sum of the factors of 21 is 32. 

Melissa P. GCSE Maths tutor, 13 plus  Maths tutor, 11 Plus Maths tuto...

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