Which of the following numbers are prime? Show why.

Question

a. 1731

b. 21977

Answer 1

1) 1731 divides evenly by 3

21977 cannot be divided by 2,3,or 5

therefore it only possible divisors are primes beginning with 7, up to half the value,

or 21977/2+1, or 10989

it turns out that it is prime, per calculator