Fatto generale: 123 is the Notation for national and international telephone numbers Recommendation ITU-T Recommendation E.123 defines a standard way to write telephone numbers, e-mail addresses, and web addresses.
Fatto matematico: 123 is the 10^{th} Lucas number.
Trivia: 123 is the telephone number of the speaking clock for the correct time in the United Kingdom.
Data storica: May 2nd is the day in 1920 that the first game of the Negro National League baseball is played in Indianapolis, Indiana.