Number Gossip

(Enter a number and I'll tell you everything you wanted to know about it but were afraid to ask.)

Unique Properties of 19

  • 19 is the side length of the Go board
  • 19 is the largest prime which is a palindrome in Roman numerals
  • 19 is the smallest number n such that nn is pandigital (contains all 10 digits)
  • 19 is the smallest prime which when turned upside down yields a different prime (61)
  • 19 is the smallest prime with a digital root of 1
  • The 19th Fibonacci number is the smallest composite Fibonacci number with a prime index
  • 19 is the smallest prime that has the same digit sum as its square
  • 19 is the only number n for which there is no multi-digit palindrome whose digit sum and beginning are both n
  • 19 is the smallest prime whose reversal is composite
  • 19 is the only prime which is equal to the difference of two cubes of primes
  • 19 is the maximum number of 4th powers needed to sum to any positive integer
  • 19 is the smallest number that is equal to the product of its digits plus the sum of its digits

Common Properties of 19