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23 is a prime number from 1-100. 23 has two factors, 1 and 23. 23 is said to also be one of the numbers that when you add up its digits, you get a prime number. It is the ninth prime number, and the ninth prime number from 1-100.

Proofs

  • Yes — 23 can be divided by 1.
  • No — 23 cannot be divided by 2-22.
  • Yes — 23 can be divided by 23.
  • Therefore, 23 has 2 factors.

As an Exponent of Mersenne Number

223 - 1, which is the number 8,388,607, can be factored into 47 x 178,481, and therefore not a prime number.

Relationships with other odd numbers

The numbers before

  • The previous odd number, 21, is not a prime number. It is divisible by 3 and 7.
  • The odd number previous to 21 is 19. 19 is a prime number.
    • 19 and 23 are four numbers apart; therefore, they are cousin primes.
  • The odd number previous to 19 is 17. 17 is a prime number.
    • 17 and 23 are six numbers apart; therefore, they are sexy primes.

The numbers after

  • The next odd number, 25, is not a prime number. It is a square number, being 52 = 25.
  • 27, the odd number following 25, is not a prime number. It is a cube number, being 33 = 27.
  • 29, the odd number following 27, is a prime number.
    • 23 and 29 are six numbers apart; therefore, they are sexy primes.
  • Due to the fact that 23 is not part of any twin numbers, it is considered an isolated prime.