Courses
Courses for Kids
Free study material
Free LIVE classes
More

# Which of the following is not a prime number?$A.$ 31$B.$ 61$C.$ 71$D.$ 91

Last updated date: 25th Mar 2023
Total views: 307.8k
Views today: 3.85k
As we know a prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A simple but slow method of checking the primality of a given number n, by calculating the factors of n. if the factor is only in the form of $1 \times n$ then it is prime otherwise it is not a prime.
$31 = 1 \times 31 \\ 61 = 1 \times 61 \\ 71 = 1 \times 71 \\ 91 = 1 \times 7 \times 13 \\$