Fatto matematico: 7880 is the maximum value of n so that there exist 4 denominations of stamps so that every postage from 1 to n can be paid for with at most 26 stamps.
Trivia: 7880 is a boring number.
Data storica: July 28th is the day in 1945 that a U.S. Army B-25 bomber crashes into the 79th floor of the Empire State Building killing 14 and injuring 26.