From Compsci.ca Wiki
42 is the ultimate answer to the ultimate question of life, the univere, and everything; as calculated by the computer known as "Deep Thought". The question is not known, though it is suspected that it is not 6x9; unless the answer is in base 13 which hasn't been specified. Some of the many questions put forward that seem to fit the bill are 6x7, 7x7-7, 6x9-14, or 2x(6+5+4+3+2+1) and really any other expression that equals 42. It is also believed that the answer and the question can not exist together in the same universe, speculation suggests that if placed together they would annihilate each other probably taking the universe with them.