Number Gossip

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Unique Properties of 11

  • 11 is the smallest prime such that 2p-1 is not prime
  • 11 is the largest number which is not expressible as the sum of two composite numbers
  • 11 is the smallest prime for which the sum of digits equals the number of digits
  • 11 is the only prime comprising an even number of identical digits
  • 11 is the smallest strobogrammatic prime
  • 11 is the only palindromic prime with an even number of digits
  • 11 is the only prime whose period length is two
  • 11 divides all palindromes with an even number of digits

Rare Properties of 11

Palindromic prime
Repunit

Common Properties of 11

Deficient
Lazy caterer
Odd
Odious
Palindrome
Prime
Square-free
Twin
Ulam