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Did you notice anything weird about the numbers 13 and 19 in the last section?
 

1 x 13 = 13 1 x 19 = 19


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
two factors:
1 and itself.


The other numbers that we could get with more than one way are called " composite."

A composite number has
more than two factors.


So, if you can find anything else that goes into a number other than 1 and itself, then it's a composite number.
 

Is 27,498 a composite number?

Yes! It's even so 2 goes in!
 

The number 1 is special.  It only has one factor -- just itself!  So, 1 is neither prime nor composite.