# Is 305 a prime number?

It is possible to find out using mathematical methods whether a given integer is a prime number or not.

For 305, the answer is: No, 305 is not a prime number.

The list of all positive divisors (i.e., the list of all integers that divide 305) is as follows: 1, 5, 61, 305.

For 305 to be a prime number, it would have been required that 305 has only two divisors, i.e., itself and 1.

Find out more:

Actually, one can immediately see that 305 cannot be prime, because 5 is one of its divisors: indeed, a number ending with 0 or 5 has necessarily 5 among its divisors.
The last digit of 305 is 5, so it is divisible by 5 and is therefore *not* prime.

As a consequence:

For 305 to be a prime number, it would have been required that 305 has only two divisors, i.e., itself and 1.

However, 305 is a **semiprime** (also called biprime or 2-almost-prime), because it is the product of a two non-necessarily distinct prime numbers. Indeed, 305 = 5 x 61, where 5 and 61 are both prime numbers.

### Is 305 a deficient number?

Yes, 305 is a deficient number, that is to say 305 is a natural number that is strictly larger than the sum of its proper divisors, i.e., the divisors of 305 without 305 itself (that is 1 + 5 + 61 = 67).