12 consists of a ten and two ones.

13 consists of a ten and three ones.

14 consists of a ten and four ones.

15 consists of a ten and five ones.

16 consists of a ten and six ones.

17 consists of a ten and seven ones.

18 consists of a ten and eight ones.

19 consists of a ten and nine ones.

The number of digits of a natural number is called the number of digits. For example, the number 9 contains only one number, so 9 is a number; Five digits 12345 contains five digits: one, ten, hundred, thousand and ten thousand.

Extended data:

First, the concept of difference:

1, number

"Number" refers to the position occupied by each digit of a number. From the right, the first digit in the numerical sequence table is "unit", the second digit is "ten digits", the third digit is "hundred digits", the fourth digit is "thousand digits", the fifth digit is "ten thousand digits", and so on.

The same number represents different values because of different digits. For example, if Arabic numerals are used to represent numbers, the same' 6' in the tenth place is six tens, in the hundredth place is six hundred, in the hundredth place is six hundred, and in the hundredth place is six hundred million.

2. Number of digits

"Number of digits" refers to the number of digits contained in natural numbers. Numbers like 458 are composed of three numbers, each of which occupies one place, so we call it three digits. 198023456 consists of nine digits, so it is nine digits. "Numbers" and "digits" cannot be confused.

Second, the meaning of numbers

The decimal counting method is characterized by "full 10 into one". In other words, every 10 unit forms a higher unit adjacent to it. That is, 10 is called "ten", 10 is called "hundred", 10 is called "thousand" and 10 is called "ten thousand".

One (a), ten, hundred, thousand, ten thousand, one hundred thousand, one million (trillion), ten million, one billion, ten billion, one hundred billion ... are all units of counting.

Numbers mean that when writing numbers, the numbers are arranged side by side in a line, and each number occupies a position. These positions are called numbers. Starting from the right end, the first place is the unit, the second place is the tenth place, the third place is the hundred places, the fourth place is the thousand places, and the fifth place is the ten thousand places, and so on. This shows that the concept of counting unit and number is different.

However, their relationship is very close. "4" means four hundred in hundreds, "7" means seven tens in tens, and "5" means five ones in tens.

Baidu Encyclopedia-Numbers