In the summer of 1964 three Pomona College students, Laurie Mets, Bruce Elgin and Buck Lawrence, tested whether one number turned up in nature more often than chance predicted. They chose forty-seven because it was a large prime expected to be rare, and it was not. Statistics professor Donald Bentley, told of the result, produced a mock proof that all numbers equal forty-seven. The joke outgrew the classroom into a standing club, the 47 Society, which still logs sightings of the number today.
The habit left campus with a 1979 graduate, Joe Menosky, who joined the writing staff of Star Trek: The Next Generation in its fourth season and began working forty-seven into scripts as a private joke carried over from college. Other writers picked it up, and the number recurred across The Next Generation, Deep Space Nine and Voyager long after any one writer's run ended. Every primary account of the origin, the Society's own history and the college's alumni magazine among them, is explicit and dated: this is a manufactured tradition with a known birthday, not a claim about the number.
Mathematically forty-seven is ordinary: the fifteenth prime, and a safe prime because twenty-three, half of forty-six, is prime as well. Digit-sum numerology reduces it to eleven, a number that system reads as a master number of heightened intuition, and only then to two. Neither the Bible's Psalm 47 nor the Quran's forty-seventh surah, named for Muhammad, attaches any meaning to the count itself; both hold the number by ordinary chapter order. This entry carries more citation than most of its neighbors only because more has reliably been written about this one number. The completeness is the paper trail, not a claim.
Sources The Origin of 47 at Pomona CollegeThe 47 Society with The Mystery of 47Pomona College Magazine, Joe Menosky (Wikipedia)Wikipedia contributors, 47 (number) (Wikipedia)Wikipedia contributors, Prime Curios! 47Chris Caldwell (The Prime Pages), The Holy BibleAnonymous (multiple authors), The Study Quran: A New Translation and CommentarySeyyed Hossein Nasr (editor-in-chief)