Prime Number:  A number that has only itself and 1 as a factor

 
1 or one:  Is not a prime number since its only factor is 1
                   (every number has 1 as a factor)
 

Primes:  2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31 ...

                for example  13 = 1 x 13
                                       29 = 1 x 29 (factors are 1 and 29)