2, a natural number, is also a positive integer between 1 and 3, and also an even number.

2, there are many mathematical properties. If a number is divisible by 2, it is even, and vice versa.

2 is the smallest prime number (also called prime number), which is a "unique" even prime number with only 1 and 2 factors, and it is a rational number. It is also an even number. 2 is also a sig number.

Generally, when using ordinal numbers, we should use "two", which is pronounced as èr in pinyin.

The mathematical differences between Chinese characters and Arabic numerals are as follows:

1. Numeric form of Chinese characters: the inherent writing form of Chinese. The basic symbols are "zero, three, four, five, six, seven, eight, nine, ten, one hundred thousand, ten thousand, one hundred million" and so on.

2. Arabic numeral form: 1 Since the end of the 9th century and the beginning of the 20th century, with the spread of western learning and the modernization process in China, Chinese has been gradually introduced, and the basic symbols are "0,1,2, 3, 4, 5, 6, 7, 8, 9" and so on.

3. In actual use, Arabic numerals can also use auxiliary symbols such as decimal point, multi-digit section break, short line and separator ":"as needed. Numbers written in Chinese characters do not contain other auxiliary symbols.

4. It can be seen that there is a general correspondence between the above two expressions of numbers and the main expression functions of numbers. When emphasizing accurate measurement and numbering functions, Arabic numerals tend to be used. Chinese characters tend to be in the form of numbers as the general purpose of characters and the occasion of representing approximate numbers.

However, this division of labor is not absolute. On the one hand, Chinese characters and numbers also have the functions of measurement and numbering. Before Arabic numerals entered China, China people used their own writing forms of Chinese numerals to count, including counting, numbering and sorting.

6. On the other hand, in the process of using Arabic numerals, their expression functions are gradually broadened, from the beginning, they are mainly used for accurate measurement to various numbering functions, and then combined with Chinese characters to express approximate numbers.

7. In this way, the two can be used interchangeably in some situations. It is precisely for this reason that it is necessary to properly standardize the two digital writing forms, and make different expressions correspond to different expression functions as far as possible, so as to achieve the goal of clear division of labor between Chinese characters and Arabic numerals and improve the efficiency of transmitting information in Chinese texts as a whole.