Find the greatest common factor quiz. The factors of a number are all numbers that that number can be divided by. Prime numbers as a rule of thumb have only two factors, one and itself; although all of them are odd, the only exception is two. To get the list of factors of a number, try dividing a series of numbers by that number and find out those that divide without a remainder. Write out a list of those numbers and do so for the other number that is provided. Find similar factors that appear in both. The largest common fact is the L.C.M. This quiz on L.C.M. is for students in 5th, 6th and 7th grades.