Prime number

A prime number is a number with a certain universally recognizable characteristic. A Prime is a natural number that has exactly two distinct natural number divisors: 1  and itself. The first twenty-five prime numbers are:

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97.

When captured by unknown aliens, Captain Jean-Luc Picard signaled the first six prime numbers by pushing the same button in sequence, hoping to prove to his captors that he was intelligent. 

Astronomers on Kelemane's planet also signaled prime numbers to the "Sky Ship" in an effort to communicate.