How to Find Factors of a Number In this lesson, let’s learn how we find factors of a number. What are factors? Anytime we have a number which is a product, we can look at which whole numbers can be multiplied to give you that product. For example, if the product is 10, I can multiply two and five which are both whole numbers to give me 10. Two and five are both called factors of 10. Second, the product is always divisible by its factors. For example, 10 can be divided by two to give me five and 10 can also be divided by five to give me another whole number two. So, the key thing to remember is a number can be divided by each one of its factors to give other whole numbers and two whole numbers that can be multiplied to give us that product are called factors of the product. Let’s use this to find factors of 20. First, what we do is we figure out which two numbers when multiplied will give us 20. One multiplied by 20 will give us 20, two multiplied by 10 will give us 20, four multiplied by five will give us 20. The factors of 20 are one, two, four, five, 10 and 20. Key thing to remember, every number can be divided by one and by itself. These are definite factors anyway and what we found was there we're four other factors. Let’s try and do 17. If we want to look at 17, what number when multiplied by each other will give us 17? I can only find one pair, one and 17. Seventeen cannot be divided by anything else other than itself and one. The factors of 17 are one and 17. When a number can only be divided by itself and one, when it only has two factors, it’s called a prime number. One other thing to remember is I can take any number for example 12, the factors of 12 would be one, two, three, four, six and 12. Out of these, two and three are primed numbers. Prime factorization of 12 will be 2×2×3. It’s written as a product of its prime factors, 2×2 is 4×3 is 12.