A factor is defined as a number that goes into another number evenly.  For example, the factors of 12 are 1, 12, 2, 6, 3 and 4. Keep in mind to always list the factors in their proper pairs. You should start with 1 and the number and then proceed upwards. You don’t need to put them in proper order while looking at the answer choices. Also, never skip any number. Start from 1 and proceed to 2 whether it works or not, then 3 and so on.  Always keep in mind the number 1 and the number itself. As these are the factors of every number including primes.