Determining if $973$ is prime 
Without a calculator, determine if $973$ is prime or not

I was given this question to solve. I know $973$ is not prime. I was told a strategy to solve whether a number is prime or not is to test all the numbers less than the square root of $973$
So I would have to test till $32$
and i find $1,7,139$ and $973$ are factors of this number.  Basically, what I want to find out is are there any other strategies to solve this question? then i wouldn't have to check till 1-32 to see if any of the numbers are factors. 

Another way, $973 = 910+63$
This gives $973 = 7.(130+9) = 7 . 139$
