The largest convention number, also known as the largest common divisor, the largest common factor, refers to two or more integer numbers total about one of the number. The maximum convention number of a, b is denoted as (a, b), similarly, the maximum convention number of a, b, c is denoted as (a, b, c), and the maximum convention number of multiple integer numbers has the same notation. There are many methods to obtain the maximum convention number, the common divisor decomposition method, short division method, shifting division method, more phase reduction method. The concept corresponding to the maximum convention number is the minimum common multiple number, a, b The minimum common multiple number is denoted as [a, b].