The mathematical constant e_1 is often referred to as Euler's number, denoted as e . It is an irrational number approximately equal to 2.71828. This constant is fundamental in various areas of mathematics, particularly in calculus, where it serves as the base for natural logarithms. In addition to its mathematical significance, e appears in many real-world applications, such as compound interest calculations in finance and in the modeling of population growth in biology. Its unique properties make it essential for understanding exponential growth and decay processes.