There is some opinion Pi isn't as important a number as 2 times pi or 6.28 which is called Tau. It turns out Tau is obtained by dividing a circle's circumference by its radius instead of dividing by its diameter as with Pi. Apparently using Tau instead of Pi makes trigonometry easier. There are calculators that have included Tau as a function. Tau Day on June 28th is celebrated in some quarters. Here are resources for Tau, will you be celebrating on Tau Day along with Pi Day?: The Tau Manifesto: https://tauday.com/ Tau Day as a Fun Holiday: https://www.timeanddate.com/holidays/fun/tau-day WSJ article which is really funny but unfortunately behind a paywall: https://www.wsj.com/articles/for-math-fans-nothing-can-spoil-pi-dayexcept-maybe-tau-day-11584123031

Nice. For some odd reason it occurred to me that other day that since all trig is about the radius, shouldn't pi be doubled rather than proportioned against the diameter. Freaky post.... I would however say that e is the rockstar of mathematical constants.