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Unique Properties of 641

  • 641 is the smallest prime factor of 2(25)+1
  • 641 is the smallest prime that remains prime after two applications of the following operation: replacing each digit d with d copies of the digit d (prime 641 to prime 66666644441, then to prime 66666666666666666666666666666666666644444444444444441

Common Properties of 641

Deficient
Odd
Odious
Prime
Square-free
Twin