A prime number is any positive integer greater than zero that has only two proper divisorsNumber that when divided into another number leaves no remainder., \(1\) and the number itself. Thus the lowest prime number is \(2\), which is also the only even prime;[a]One is not a prime number because it has only one proper divisor, itself. numbers greater than \(1\) that are not prime are known as composite numbers, because they can be expressed as the product of two other numbers smaller than themselves;[1] for instance, \(8\) can be expressed as \(2 \times 4\).
Prime numbers are fundamental to mathematics, as all whole numbers can be constructed from them; anything that can be shown to be true about prime numbers is therefore true for all numbers.[2]
Two numbers are considered to be relatively prime, or coprime, if their greatest common divisor is \(1\). For example, \(9\) and \(28\) are coprime, despite neither being a prime number.[3]
Notes
| a | One is not a prime number because it has only one proper divisor, itself. |
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