1, the characteristics of multiples of a number: the number of multiples of a number is infinite, in which the minimum multiple is itself and there is no maximum multiple; If several numbers are multiples of a number, then the sum of these numbers is also a multiple of this number.

2. In integer division, if the quotient is an integer without remainder, we say that the dividend is a multiple of the divisor, and the divisor is a factor of the dividend.

Generally, if a is an integer, even numbers can be represented by 2a. Odd numbers can be represented by 2a+ 1.

4. Among natural numbers, numbers that are multiples of 2 are called even numbers (0 is also even numbers), and numbers that are not multiples of 2 are called odd numbers. The smallest even number is 0 and the smallest odd number is 1.

5, a number, if only 1 and its own two factors, such a number is called a prime number (or prime number); 1 is neither prime nor composite.