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I never read the book, but I read this somewhere online, so it might as well be a fan theory but it goes something like this:

if you add all the numbers in the word math m+1+t+h each letter being in the order they appear in the alphabet they should add up to 42.

Haha, interesting and a little cabalistic... reminds me of the movie "Pi" :D but Douglas Adams makes it more funny for understanding :D