Is 399 a Prime Number?

To determine whether the number 399 is a prime number, it is necessary to check if it has any divisors besides 1 and itself. This involves checking if there are any other numbers that can divide 399 evenly, meaning without leaving a remainder. If such divisors exist, 399 is not a prime number; otherwise, it would be classified as prime.

To quickly check if 399 is a prime number:

Calculate the square root of 399

$\sqrt{399} = 19.97$

Prime numbers less than or equal to 19.97: 2, 3, 5, 7, 11, 13, 17, 19

• 399 is divisible by number: 3, 7, 19.

Since 399 is divisible by a number 3, 7, 19 other than 1 and itself, so it is not a prime number