What is the sum of the factors of 21?

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

Answered by Melissa P. Maths tutor

53301 Views

See similar Maths 11 Plus tutors

Related Maths 11 Plus answers

All answers ▸

There are 2 green jelly beans, 5 are yellow and 13 are red. Sue picks one jelly bean. What is the possibility that sue pick a jelly bean that is not yellow?


There are 25 CD's in a box and an individual orders 14 boxes. How many CD's did the person order in total


Textbooks are stored on 2 shelves. Each shelf is 0.72m long and each textbook is 30mm wide. Can 50 textbooks be stored on these 2 shelves?


how do you calculate a percentage of a number?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences