What was the significance of the number?

It's the meaning of life.

I've just finished the audiobook (narrated by Stephen Fry - highly recommended.)
It is never resolved what the significance is. The search then turns to what the question is and finally the mice (who financed the research) just made some shit up in order to have a question that fits the answer.

How many roads must a man walk down?
42.

I think the significance is that the question is what is 7 times 7

and the answer isn't 42, which explains why everything has been slightly 'wrong' with the universe