I hate you... -__-bringer of illumination said:HHGTTG is an UHMAZING BUUUUUUUUUUUUUUK
(over 9000 cookies if you get the obscure internet reference)
As for those who say that it is 6*9 because of the scrabble-bag test... you didn't read the book good enough. Remember, humans as we know it never came from Earth in the first place. Those stupid phone cleaners, hair stylists and insurance salesmen or whatnot from Golgafrincham which crashed on Earth are our forefathers. We where never a true part of the computer program. So the question he subconsciously pulled out of the bag was a distorted one.
The actual question cannot be know to anyone who know the answer either. The universe will collapse in on itself then, and be remade in something even weirder. So there. We will never know the real question. Be glad we know the answer is 42.