Fatto generale: 726 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 726 is the number of 4-step self-avoiding walks on the cubic lattice.
Trivia: 726 is a boring number.
Data storica: December 26th is the day in 1997 that the Soufriere Hills volcano on the island of Montserrat explodes, creating a small tsunami offshore.