"20" represents a mathematical data, an Arabic numeral.

1. Introduction to Arabic numerals:

Arabic numerals are commonly used internationally today. It was originally invented by the ancient Indians, then spread to Europe by the Arabs, and then modernized by the Europeans. It is precisely because of the spread of the Arabs that it became a key node for the number to be finally adopted internationally, so people call it "Arabic numerals".

2. The emergence of scientific notation:

Arabic numerals consist of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9***10 Composed of counting symbols. Use the place value method, with the high order on the left and the low order on the right, writing from left to right. With the help of some simple mathematical symbols (decimal point, negative sign, percent sign, etc.), this system can represent all rational numbers unambiguously. In order to express very large or very small numbers, people created scientific notation based on Arabic numerals.

3. Usage specifications:

Physical quantity value. The physical quantity values ??must use Arabic numerals, and the measurement units after the numbers must use my country's legal measurement units, such as: 3 kg, 45 m, 2 min, etc.

Century, year, year, month, day, time. For example: the 1990s, December 12, 2005, 16:15, etc.

The number before the counting unit. Numbers greater than 10 before the counting unit must use Arabic numerals, integers from 1 to 10. Wherever Arabic numerals can be used and are appropriate, Arabic numerals should also be used. Such as: 12 pencils, 4 tubes, 1 flower, etc.