Short answers, pulled from the story.
The number 42 is the answer to the ultimate question of life the universe and everything. The question itself remains unknown within the franchise created by Douglas Adams.
The first episode of the radio series was broadcast on the 8th of March 1978 on BBC Radio 4. The episode was titled Fits and aired at 10:30 pm.
Eoin Colfer wrote the sixth novel And Another Thing... with additional unpublished material by Douglas Adams. The book was published in October 2009.
The film was released in the United States and Canada on the 29th of April 2005. It had a London premiere on the 20th of April 2005 and was released in the UK and Australia on the 28th of April 2005.
Douglas Adams claimed the title came from a 1971 incident while he was hitchhiking around Europe with a copy of the Hitch-hiker's Guide to Europe book. He later stated that he reassembled the memory from telling the story many times.
The novels were translated into more than 30 languages by 2005. The book version of The Hitchhiker's Guide to the Galaxy has sold over 14 million copies as of 2005.