Let’s choose the number 12. Write this number down on a piece of scratch paper.
In our example, 12 has multiple factors - 12 × 1, 6 × 2, and 3 × 4 all equal 12. So, we can say that 12’s factors are 1, 2, 3, 4, 6, and 12. For our purposes, let’s work with the factors 6 and 2. Even numbers are especially easy to factor because every even number has 2 as a factor. 4 = 2 × 2, 26 = 13 × 2, etc.
For instance, in our example, we have reduced 12 to 2 × 6. Notice that 6 has its own factors - 3 × 2 = 6. Thus, we can say that 12 = 2 × (3 × 2).
In our example, we’ve reduced 12 to 2 × (2 × 3). 2, 2, and 3 are all prime numbers. If we were to factor further, we’d have to factor to (2 × 1) × ((2 × 1)(3 × 1)), which isn’t typically useful, so it’s usually avoided.
For example, let’s factor -60. See below: -60 = -10 × 6 -60 = (-5 × 2) × 6 -60 = (-5 × 2) × (3 × 2) -60 = -5 × 2 × 3 × 2. Note that having an odd number of negative numbers besides one will give the same product. For example, -5 × 2 × -3 × -2 also equals 60.
For the purpose of our example, let’s choose a 4-digit number to factor - 6,552.
In our example, since 6,552 is even, we know that 2 is its smallest prime factor. 6,552 ÷ 2 = 3,276. In the left column, we’ll write 2, and in the right column, write 3,276.
Let’s continue with our process. 3,276 ÷ 2 = 1,638, so att the bottom of the left column, we’ll write another 2, and at the bottom of the right column, we’ll write 1,638. 1,638 ÷ 2 = 819, so we’ll write 2 and 819 at the bottom of the two columns as before.
In our example, we’ve reached 819. 819 is odd, so 2 is not a factor of 819. Instead of writing down another 2, we’ll try the next prime number: 3. 819 ÷ 3 = 273 with no remainder, so we’ll write down 3 and 273. When guessing factors, you should try all prime numbers up to the square root of the largest factor found so far. If none of the factors you try up to this point divide evenly, you’re probably trying to factor a prime number and thus are finished with the factoring process.
Let’s finish factoring our number. See below for a detailed breakdown: Divide by 3 again: 273 ÷ 3 = 91, no remainder, so we’ll write down 3 and 91. Let’s try 3 again: 91 doesn’t have 3 as a factor, nor does it have the next lowest prime (5) as a factor, but 91 ÷ 7 = 13, with no remainder, so we’ll write down 7 and 13. Let’s try 7 again: 13 doesn’t have 7 as a factor, or 11 (the next prime), but it does have itself as a factor: 13 ÷ 13 = 1. So, to finish our table, we’ll write down 13 and 1. We can finally stop factoring.
In our example 6,552 = 23 × 32 × 7 × 13. This is the complete factorization of 6,552 into prime numbers. No matter what order these numbers are multiplied in, the product will be 6,552.
