Question 851502:  what is the greatest prime you must consider to test whether 1042 is prime 
 Answer by Edwin McCravy(20064)      (Show Source): 
You can  put this solution on YOUR website! We know right off that 1042 is not prime because it is even. 
We divide it by the smallest prime, which is 2, and we get 521, 
so it isn't prime.  Incidentally, 521 happens to be prime, but  
we only needed to try 2.
 
Answer: 2.  
 
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