Divisor

Cuisenaire ten

Highly composite numbers

Lattice of the divisibility of 60; factors

Divisor in mathematics, specifically in the field of number theory, is an integer that can be multiplied by another integer to yield a given integer. The concept of divisors is fundamental in understanding the structure and properties of integers, especially in the realms of prime numbers and factorization. This article delves into the definition, properties, and significance of divisors in mathematics.

Definition

A divisor of an integer n, also known as a factor of n, is an integer d such that there exists an integer m where d × m = n. In this context, n is said to be divisible by d, and we can also say that d divides n, denoted as d | n. For every integer n, 1 and n (itself) are always divisors of n. If a divisor of n is neither 1 nor n itself, it is called a proper divisor.

Properties

• Divisibility: This is a key concept in understanding divisors. If d is a divisor of n, then all multiples of d are also divisors of n.
• Prime Divisors: A prime number has exactly two distinct divisors: 1 and itself. Prime divisors play a crucial role in the fundamental theorem of arithmetic, which states that every integer greater than 1 is either a prime itself or can be uniquely factored as a product of prime numbers, up to the order of the factors.
• Greatest Common Divisor (GCD): The GCD of two integers is the largest integer that divides both of them without leaving a remainder. The concept of GCD is essential in simplifying fractions and solving Diophantine equations.
• Least Common Multiple (LCM): The LCM of two integers is the smallest positive integer that is divisible by both. It is directly related to divisors through the formula involving the product of the numbers and their GCD.

Significance

Divisors are central to many areas of mathematics and its applications:

• In cryptography, particularly in the RSA algorithm, the factorization of large numbers into prime divisors is a fundamental operation.
• In number theory, divisors are used to define and study perfect numbers, amicable numbers, and other special number classes.
• Divisors also play a role in algebraic geometry, particularly in the definition and properties of divisors on algebraic curves.

See Also

• Prime number
• Factorization
• Greatest common divisor
• Least common multiple
• Fundamental theorem of arithmetic