"π has fascinated mathematicians, engineers and other people for centuries. It is a mathematical constant that is the ratio of a circle's circumference (C) to its diameter (d); This also explains why and how this number got its name: the lowercase π was first adopted in 1706 as an abbreviation for this number because it is the first letter of the Greek for "perimeter", specifically of a circle." Introduces a video by Numberphile explaining more about the determination of π
"An average person can read out approximately 120 digits/min. Keeping this pace it would take more than 158,000 years to recite the 10 trillion digits of π discovered this year and roughly 3 weeks to read out the 4 million digits visualized here."