Least Common Multiple (LCM), if there is a natural number a that is divisible by a natural number b, then a is called a multiple of b, and b is a divisor of a. For two integers, it refers to the smallest common multiple of the two numbers. When calculating the least common multiple, the greatest common divisor is usually used to assist the calculation.

The greatest common divisor, also known as the greatest common factor, refers to the largest common divisor shared by two or more integers. The greatest common divisor of a and b is recorded as (a, b). Similarly, the greatest common divisor of a, b, and c is recorded as (a, b, c). The greatest common divisor of multiple integers also has the same notation. There are many ways to find the greatest common divisor. The most common ones are prime factorization, short division, Euclidean algorithm, and subtraction method. The concept corresponding to the greatest common divisor is the least common multiple. The least common multiple of a and b is recorded as [a, b].