# Thread: which numbers are prime

1. ## which numbers are prime

which numbers are prime?

a. 667

b. 557

i tried using numbers like (23)^2

and (24)^2

I didn't know how to prove this. Please show what needs to be done.

2. Originally Posted by rcmango
which numbers are prime?

a. 667

b. 557

i tried using numbers like (23)^2

and (24)^2

I didn't know how to prove this. Please show what needs to be done.
Try factoring them.

For example, divide 667 by 2. It gives a decimal. So try 667/3, 667/5, 667/7 until you get to about $\sqrt{667}$. If you have no factors yet, then the number is prime.

I get that 557 is prime and 667 is composite.

-Dan

3. okay, 667 = 23 * 29

thankyou for the help.