Definition of Prime Number

A prime number is any number whose only factors are 1 and itself.
Contrast composite numbers with composite numbers.

Some often-confused facts about prime numbers

  • 0, zero, is not a prime a number
  • 1 is also not a prime number. Although the definition of a prime number seems to apply to 1, you have to count 1 twice --sorry no 'double dipping' for prime numbers. 1 is not prime.
  • 2 : The only even prime number is 2, because all of the other even prime numbers are multiples of 2 and therefore violate the definition of a prime number (only divisible by 1 and itself)
  • Read more about how to determine if a number is prime

Examples of prime numbers

  • 2 is prime because its only factors are 1 and 2 ( 2 is the only even prime number.)
  • 5 is prime because its only factors are 1 and 5
  • 7 is prime because its only factors are 1 and 7

    NON Examples of prime numbers

    (they're prime)
  • 6 is not prime because its factors are factors are 1 ,2, 3, 6
  • 51 is not prime because its factors are factors are 1 , 3 , 17, 51
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