Question 1208631
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To check whether 4755 is a prime, you should test all primes lesser than {{{sqrt(4755)}}} = 68.95... 


The greatest prime from this list is 67.



Why it is so, read and learn from these Internet links


https://en.wikipedia.org/wiki/Primality_test


https://en.wikipedia.org/wiki/Primality_test



or read any fundamental course on Number theory.