# 01 What is Euler’s number e?

e (mathematical constant) – Wikipedia

Euler’s number, denoted by the symbol e {\displaystyle e}, is a constant that plays a central role in all of calculus and all related branches of mathematics, especially in differential and integral calculus, but also in stochastics (combinatorics, normal distribution).

Its numeric value is approximately 2.71828 18284 59045 23536 028

The number was named after the Swiss mathematician Leonhard Euler, who described numerous properties of e. Occasionally, it is also called Napier’s constant (or Neper’s constant) after the Scottish mathematician John Napier. It is one of the most important constants in mathematics.

There is an international day of the Eulerian number e. In countries where, as in Germany, the day is written before the month (1/27) for the date, it is on January 27. In countries where, as in the USA, the month is written before the day (2/7), it is on February 7.