A factor of a number is a whole number that divides evenly into the other number. So, when you divide by the factor the remainder is zero. Factors come in pairs. When you divide a number by one of its factors, the answer or quotient is the paired factor.
Is 4 a factor of 36 ?
Yes, 36 divided by 4 gives us an answer of 9 with no remainder.
Is 3 a factor of 47 ?
No, 47 divided by 3 gives us an answer of 15 with a remainder of 2.