It may seem irrational to some, but we celebrate the number pi (π) every year on March 14, since 3/14 represent the first three digits of pi's decimal expansion.
NBC News reports that pi is more than just a good excuse to eat pie in the middle of March. It characterizes the perfect circle in a Platonic world, because it represents the constant ratio of the circumference to the diameter.
U.S. & World
But it does more than that, too. Pi is part of Heisenberg's uncertainty principle and a formula that prices risk.
It's captured the popular imagination with its irrationality, which means it can't be represented as a fraction. A computer calculated pi down to the 22,459,157,718,361st decimal place, while Rajveer Meena from India has a Guinness Book world record for reciting 70,000 of those decimal places.