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661 is a prime number from 601-700. 661 has 2 factors, 1 and 661. It is the 121st prime number, and the twelfth prime number from 601-700. 661 can be turned upside down to give 199, which is also a prime number. 
661

Proofs

  • Yes — 661 can be divided by 1.
  • No — 661 cannot be divided by 2-660.
  • Yes — 661 can be divided by 661.

Relationship with other odd numbers

The numbers before

  • The previous prime number is 659.
    • There are no odd numbers between 659 and 661. As a result, they are twin primes.
  • The previous prime number before 659 is 653.

The numbers after

  • The next prime number is 673.
    • Notably, 667 is the product of 23 and 29, while 671 is divisible by 11. They are both composite numbers.
  • 677 is the next prime number after 673.

Trivia

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