What is HCF? HCF stands for ‘Highest common factor.’ A factor is a smaller number that you use to multiply other numbers. Don’t get it confused with Least common multiple, which means you have to list the multiples, eg 6, 12, 18, 24, 30.
For example, what is the HCF of 12 and 18?
12 {1, 2, 3, 4, 6, 12}
18 {1, 2, 3, 6, 9, 18}
A common factor means a factor that appears in both numbers. But we want the highest common factor, which is 6. Therefore, the HCF of 12 and 18 is 6.