3.1415926535897932384626433 That is as far as I can memorize. 25 digits. A fact about pi:
The decimal representation of Ï truncated to 11 decimal places is good enough to estimate the circumference of any circle that fits inside the Earth with an error of less than one millimeter, and the decimal representation of Ï truncated to 39 decimal places is sufficient to estimate the circumference of any circle that fits in the observable universe with precision comparable to the radius of a hydrogen atom.