Fatto generale: 220 is the common voltage in many countries.
Fatto matematico: 220 is a tetrahedral number, the sum of the first ten triangular numbers.
Trivia: 220 is the common voltage in many countries.
Data storica: August 7th is the day in 1974 that Philippe Petit performs a high wire act between the twin towers of the World Trade Center 1,368 feet (417 m) in the air.