Prime Number Checker

Determine if a number is prime or composite

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Enter a number to see its classification.

Understanding Prime Numbers

What is a Prime Number?

A **prime number** is a natural number greater than 1 that has no positive divisors other than 1 and itself. In other words, it cannot be formed by multiplying two smaller natural numbers.

Example Primes: 2, 3, 5, 7, 11, 13, 17, 19...

Numbers that are not prime (and are greater than 1) are called **composite numbers**.

Is 1 a Prime Number?

No, **1 is not a prime number**. By definition, a prime number must have exactly two distinct factors: 1 and itself. Since 1 only has one factor (itself), it doesn't fit the criteria.

Key Properties

The number **2** is the only even prime number.
All primes greater than 3 can be written in the form 6k ± 1.
There are infinitely many prime numbers.

Frequently Asked Questions

The simplest way is trial division: check if the number is divisible by any integer from 2 up to its square root. If no divisors are found, the number is prime.

No, the term "prime number" is strictly defined for positive integers (natural numbers) greater than 1.

Factoring Hint

If a number ends in 0, 2, 4, 6, or 8, it's divisible by 2. If its digits add up to a multiple of 3, it's divisible by 3!

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