Fatto generale: 40 is the number of years of marriage as the ruby wedding anniversary.
Fatto matematico: 40 is a repdigit in base 3 (1111) and a Harshad number in base 10.
Trivia: 40 is the number of weeks for an average term of pregnancy, counting from the woman’s last menstrual period.
Data storica: February 9th is the day in 1964 that the Beatles make their first appearance on The Ed Sullivan Show, performing before a "record-busting" audience of 73 million viewers.