621
xkcd #2922: Pub Trivia
(imgs.xkcd.com)
Alt text:
Bonus question: Where is London located? (a) The British Isles (b) Great Britain and Northern Ireland (c) The UK (d) Europe (or 'the EU') (e) Greater London
8 is the sum of 5+3 both of which are primes. I think the Conjecture just states that there is a sum of two primes not every sum consists only of primes
Ah gotcha! I thought it meant exclusively prime numbers