# 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 n
^{n}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
- A hexahexaflexagon is made from a strip consisting of 19 equilateral triangles
- 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
- The second repunit prime has 19 digits
- 19 is the smallest prime ending in a composite digit
- 19 is the smallest number sandwiched between two numbers that are products of 3 primes