""An Arithmetical Theory of Certain Numerical Functions"" is a book written by Eric Temple Bell and published in 1915. The book focuses on the study of certain numerical functions and their properties using arithmetical methods. The functions discussed in the book include the divisor function, the sum-of-divisors function, the Euler phi function, the Mertens function, and the Liouville function. The book begins with an introduction to the theory of...