The number 60 has the following factors: 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60, -1, -2, -3, -4, -5, -6, -10, -12, -15, -20, -30 and -60. For 60 to have a common factor, another number must exist in the mathematical question. Factors are numbers multiplied together to obtain the desired number. Common factors of numbers are factors that both numbers have in common.

To find the common factors of two or more numbers, first find the factors of each number. Then, look to see what factors all numbers have in common. A problem may ask the solver to find the common factors of 20 and 25. First, it is necessary to find the factors of 20, which are 1, 2, 4, 5, and 20 Then, find the factors of 25, which are 1, 5, and 25. Finally, look at which factors both numbers have in common. In this case, those numbers are 1 and 5. Some math problems ask to find the largest common factors of numbers. This is also known as the greatest common factor, which is simply the largest number both numbers have in common as a factor. In the case of 20 and 25, the greatest common factor is 5.