2 , 3 , 5 , 7 13 , 17, 19 , 23 , 29 . . . are all prime numbers
All prime numbers have two factors: one and itself. (For example, the factors of 11 are 1 and 11.)
210 is the number whose prime factors are the first four primes unrepeated.
A prime number has exactly two factors, 1 and the number itself.
1 and 2