# 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 13

- 13 is widely known as the unlucky number (it also happens to be a Lucky number)
- 13 is the smallest prime which is not a minimal prime
- Three planes can cut a donut (solid torus) into a maximum of 13 parts
- 13 is the smallest prime which can be represented as sum of two primes (i.e., 2 + 11) as well as sum of two composite numbers (i.e., 9 + 4)
- 13 is the smallest emirp
- 13 is the smallest prime whose sum of digits is square
- 13 is the number of Archimedian solids
- Unreasoned fear of the number 13 is termed triskaidekaphobia
- 13 is the number of times in one century when the date in the format month day and the last two digits of the year can be written with the same digit
- 13 is the number of intersections of diagonals inside a regular hexagon
- 13 is the smallest prime p such that its cube contains the next prime after p as a substring