620
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
I screwed up twice here. Forgot 2 was a prime somehow.
1+4 was just a typo, meant 1+3.