@ Eric S, Zith,
I'm beginning to think we should stop typing in the first part of the XKCD URL and just the number ;)
There is an old joke about it,
A young soldier fresh out of basic training spends his first night in a new barracks.
After lights out one of the older soldiers calls out 347, and is promptly followed by hearty laughter, then another soldier calls out 27, followed by more laughter and this goes on for about an hour.
The next morning the young soldier asks one of the older soldiers what was happening. and was told "Oh just swapping jokes". With a puzzled look the young soldier says "What's funny about numbers?" To which the other soldier replied, "Ahh you don't know, well you see there's only so many jokes, and we tell them so often it saves time to just give them numbers."
The older soldier moves off leaving the young soldier with a very perplexed look.
That night after lights out the other soldiers start calling out numbers and get laughs so the young soldier decides to have a go and calls out 57, but there is no laughter, just silence till another soldier calls out 43 which gets a lot of laughs. So the young soldier tries again with "347" again no laughs until after another soldier calls out a number.
The following morning the young soldier goes to the old soldier who told him about the numbered jokes the day before, and asks "Why didn't anybody laugh when I called out a joke number last night?", the older soldier looks at him compassionately and puts his arm around the young soldiers shoulder and says ,"Well I'm sorry to say it son, but it's the way you tell them".