Fatto generale: 5 is the number of basic "pillars" of Islam.
Fatto matematico: 5 is the second Sierpinski number of the first kind, and can be written as S2=(22)+1.
Trivia: 5 is the number of interlocked rings in the symbol of the Olympic Games, representing the number of inhabited continents represented by the Olympians (counting North America and South America as one continent).
Data storica: January 5th is the day in 1945 that the Soviet Union recognizes the new pro-Soviet government of Poland.