This function applied to 10^666 gives the Leviathan number. Taking the sum of the reciprocals of this function applied to the natural numbers converges to Euler's number. The logarithm of this function's value for very large numbers can be approximated by a method named for Stirling. The gamma function extends this function to the complex plane. The number of ways to arrange n elements is given by this function of n. name this function equal to the product of all positive integers less than or equal to n, symbolized with an exclamation point.
a) Fibonacci function
b) Logarithmic function
c) Exponential function
d) Factorial function