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.

A prime number has exactly two factors, itself and one. The first ten prime numbers are \({2}\), \({3}\), \({5}\), \({7}\), \({11}\), \({13}\), \({17}\), \({19 ...