In 11-limit just intonation, 99/64 is an undecimal superfifth of about 755.2 ¢. This interval is also known as the undecimal major fifth through analogy with 16/11 being the "minor fifth" as named by Ivan Wyschnegradsky, and can additionally be somewhat similarly dubbed the Alpharabian paramajor fifth or even the just paramajor fifth. It is distinguished from the simpler 17/11 by the twosquare comma (1089/1088). Despite being relatively more complex, 99/64 is actually pretty useful as an interval for those who work more extensively with the 11-limit.
This interval is especially close to the 17th step of 27edo.