Did you notice anything weird about the numbers 13 and 19 in the last section?
There was only one way to get them! So, they each only had two factors.
When this happens, we call the number "prime."
A prime number has exactly |
The other numbers that we could get with more than one way are called " composite."
A composite number has |
So, if you can find anything else that goes into a number other than 1 and itself, then it's a composite number.
The number 1 is special. It only has one factor -- just itself! So, 1 is neither prime nor composite.