Question

Which of the following is not a prime number? A. 1057,B.3163,C.157,D.263

Answer 1

1057 is not a prime because 157 is a prime triplet and 263 comes between the 262 and 264

Answer 2

Answer:

The correct option is A. 1057 is not prime because it is divisible by 7 and 151.

Step-by-step explanation:

A number is called prime if it is only divisible by 1 or itself.

The factor form of given numbers are

$1057=1\times 7\times 151$

$3163=1\times 3163$

$157=1\times 157$

$263=1\times 263$

It is clear that the numbers 3163,157 and 263 are divisible by 1 or themselves. So, they re prime numbers.

Since 1057 is divisible by 7 and 151. Therefore 1057 is not prime and option A is correct.