A factor is a number that goes into another number. For example, 3 is a factor of 15. Factor pairs are pairs of numbers that multiply to make the number that you are factorising. 3 x 5 = 15 so {3,5} are a factor pair of 15.

Factors are really useful. You will use them when factorising quadratics, in number theory, to find the HCF and LCM of a group of numbers. It is important that you understand how to find them.

Some numbers are special because of properties of their factors. A perfect number is one in which the sum of the factors is exactly twice the number itself. Six has the factors {1, 2, 3, 6} and if you add these, 1+2+3+6=12 which is obviously double 6, so six is a perfect number.

Multiple exam type questions on calculating the prime factors of a number, HCF and LCM of a pair of numbers.

Finding factor pairs and then investigating to see which numbers are abundant, deficient or perfect.

Video on finding the product of prime factors using a factor tree.

Assessment on finding the product of prime factors in various ways based on GCSE maths type questions.

Erasothenes' Sieve for finding prime numbers. I have arranged it in rows of six so that it is obvious that above 4, all prime numbers are of the form 6n-1 or 6n+1. Obviously, not all numbers of this form are prime.

Factorising expressions of the type seen on pages 2 to 4 of the exam papers at GCSE. I emphasise the connection between dividing and factorising. It will seem a long winded way on the video, but it is good introduction as the students seem to understand what is going on better.

Factorising expressions of the type seen on pages 2 to 4 of the exam papers at GCSE.

Triangular numbers, polygonal numbers, factors and multiples, HCF and LCM, Division Algorithm, Euclid's Algorithm, Prime Numbers, Goldbach Conjecture. What is there not to love?

Ideas, definititions and things to put up on your wall about prime numbers, square numbers, Bertrand and Goldbach's Conjectures, Is one a prime?

What is a factor pair and how do you work them out? Find some questions on this subject here.

How to calculate the product of prime factors.Find some questions on this subject here.

Video on calculating lcm and hcf using factor trees and a Venn diagram.Find some questions on this subject here.

Video on calculating lcm and hcf using factor trees and a Venn diagram.Find some questions on this subject here.

Maths Questions on Prime Factors. The last four videos are designed to help with this work if you get stuck.

Prime Numbers, Prime Factors, Highest Common Factor and Lowest Common Multiple

Questions on Prime Factors, factor pairs, HCF and LCM, GCD, HCF and LCM problems, Factorising into a single bracket.