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643 is a prime number from 601-700. 643 has 2 factors, 1 and 643. It is the 117th prime number, and the eighth prime number from 601-700. 
643

Proofs

  • Yes — 643 can be divided by 1.
  • No — 643 cannot be divided by 2-642.
  • Yes — 643 can be divided by 643.

Relationship with other odd numbers

The numbers before

  • The previous prime number is 641.
    • There are no odd numbers between 641 and 643. As a result, they are twin primes.
  • The previous prime number before 641 is 631.
    • 637 is divisible by 7, therefore not a prime number.

The numbers after

  • The next prime number is 647.
    • 643 and 647 are four numbers apart; therefore, they are cousin primes.
  • 653 is the next prime number after 647.
    • 649 is divisible by 11, therefore not a prime number.

Trivia

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