As a mathematical constant, e is the basis of natural logarithmic function. Sometimes called Euler number, named after the Swiss mathematician Euler; There is also a relatively rare name Napier constant to commemorate the introduction of logarithm by Scottish mathematician John Napier.

It is one of the most important constants in mathematics, just like pi and imaginary units I and E. E is an infinite acyclic decimal and a transcendental number, and its value is about 2.7 1828.

1844, the French mathematician joseph liouville first speculated that e was a transcendental number. It was not until 1873 that the French mathematician Hermite proved that e was a transcendental number. 1727, Euler first used e as a mathematical symbol. Later, after a while, people decided to use E as the base of natural logarithm to commemorate him.

The application of e in natural science is not less than π value. For example, in atomic physics and geology, e is used to examine the decay law of radioactive materials or the age of the earth. E will also be used when Tchaikovsky's formula is used to calculate rocket speed and when calculating the optimal benefits of savings and biological reproduction.