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 15

  • 15 is the smallest emirpimes
  • 15 is the smallest composite cyclic number, that is number n with the property that there is only one group of order n
  • 15 is the magic constant of the unique order-3 normal magic square
  • 15 is the number of letters in the words "uncopyrightable" and "dermatoglyphics", which are the only two longest words there are without repeating a letter

Rare Properties of 15

Cake

Common Properties of 15

Composite
Deficient
Evil
Lucky
Odd
Square-free
Triangular