Function e returns a close approximation of the irrational constant value of e, also known as Euler's number or Napier's constant. This value is the base of natural logarithms. The e function takes no parameter so the use of parentheses is not necessary. If parentheses are used, they must remain empty.
Because constant e is an irrational value, it cannot be represented exactly using any finite number of digits. In order to reduce rounding errors, Calcute internally stores more fractional digits than it normally displays: