Modular arithmetic is used extensively in pure mathematics, where it is a cornerstone of number theory. But it also has many practical applications. It is used to calculate checksums for international standard book numbers (ISBNs) and bank identifiers (Iban numbers) and to spot errors in them.

Is modular arithmetic important?

Modular arithmetic is important in number theory, where it is a fundamental tool in the solution of Diophantine equations (particularly those restricted to integer solutions).

Why do we use modulus?

The modulus operator - or more precisely, the modulo operation - is a way to determine the remainder of a division operation. Instead of returning the result of the division, the modulo operation returns the whole number remainder. ... That remainder is what the modulo operation returns.