42

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. Some of the many questions put forward that seem to fit the bill are 6x7, 7x7-7, 6x9-14, and really any other equation that equals 42.