This issue has been controversial for a long time. Let's take a look at the description of "how many digits" on page 98 of "A Book for Mathematics Teachers in Nine-year Compulsory Education for Six-year Primary Schools": Usually, in natural numbers, numbers containing several digits are called how many digits. For example, 2 "is a number containing a number, which is called a number. "30" is a two-digit number, called a two-digit number. "405" is a three-digit number, which is called a three-digit number, but it should be noted that it is generally not said that 0 is a few digits.

Experts explained that in the theory of natural numbers, the definition of "several digits" is like this. A number represented by only one significant digit is called a single digit. A number represented by only two digits (the first digit on the left is the significant digit) is called a two-digit number. Therefore, in a number, the number of digits (the first digit on the left is the significant digit) is called the number of digits.