Fatto generale: 9797 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 9797 is the product of two consecutive primes.
Trivia: 9797 is an uninteresting number.
Data storica: October 27th is the day in 1904 that the first underground New York City Subway line opens; the system becomes the biggest in United States, and one of the biggest in world.