Fatto generale: 3 is the number of witches in William Shakespeare's Macbeth.
Fatto matematico: 3 is a triangle is the only figure which, if all endpoints have hinges, will never change its shape unless the sides themselves are bent.
Trivia: 3 is the number of points received for a successful field goal in both American football and Canadian football.
Data storica: January 3rd is the day in 1997 that China announces it will spend US$27.7 billion to fight erosion and pollution in the Yangtze and Yellow River valleys.