How many of the prime numbers between 10 and 20 can be written as the sum of two primes?

All prime numbers greater than 2 are odd numbers. For an odd prime to be written as the sum of two primes, one of the primes must be 2 because two odd primes will produce an even sum.

11 cannot be written as the sum of two primes.

13 = 2 + 11.

17 cannot be written as the sum of two primes.

19 = 2 + 17.