42.
God‘s Final Message To His Creation is written in fire in letters thirty feet high on the far side of the Quentulus Quazgar Mountains. The long path is lined with souvenir stands at spaced-out intervals.
When Marvin the robot reads the message, it says, “We apologise for the inconvenience.” However, Fenchurch‘s reaction suggests that the message she saw was the Ultimate Question of Life, the Universe and Everything (and that presumably, therefore, the Message is personalized to each viewer)