whereas 9 is not a prime number as it has three factors: 9, 3 and 1. The first 10 prime numbers are: 2, 3, 5, 7, 11, 13, 17, 19, 23 and 29. It is interesting to note that 2 is the only even prime ...

2 is the only even prime. 2 + 14 = 16. 14 has more than two factors (1, 2, 7, 14). Other pairs of even numbers adding to 16 can be ignored (4 + 12, 6 + 10 and 8 + 8), none are prime. 16 = 1 + 15.