Question

Find the largest prime number which you need to test as a divisor to find whether or not each
of the following is a prime number.
a. 329
b. 407
C. 223
d. 983
e. 491
f. 629​

Answer 1

983 is the answer because 9±8±3 = 20. 20 is not divisible by 3. So may be it is the largest prime number.