Also known as prime numbers. Refers to a natural number greater than 1, except 1 and the integer itself, which cannot be divisible by other natural numbers.

Ps: this is not standardized. . . Sweating. . . I can't express it with formulas or anything. . .

Odd number:

Among the integers, the number that is not divisible by 2 is odd, odd =2n+ 1 (or-1), where n is an integer. Odd numbers include positive and negative odd numbers.

Even number:

An integer divisible by 2 is called an even number. Even number =2n, where n is an integer.

Complex number:

Symbol c of complex number set, complex number refers to the number a+bi which can be written in the following form, where A and B are real numbers and I is imaginary unit (i.e.-1 root). Complex numbers include real numbers and imaginary numbers.

Real number:

The symbol r of real number set includes rational number and irrational number. Among them, rational numbers include integers and fractions. Irrational number is an infinite cycle decimal.

imaginary number

Imaginary number refers to a number whose square is negative, that is, when a+bi and B are not equal to zero, bi is called imaginary number. This number has a special symbol "I", which is called imaginary unit.

Rational number:

Symbol q of rational number set, rational number is the general name of integer and fraction, and all rational numbers can be converted into component numbers.

Irrational number:

That is, the real number of irrational numbers cannot be written as the ratio of two integers. If written in decimal form, there are infinitely many digits after the decimal point, which will not cycle.

integer

Integer set symbol z, numbers like -2,-1, 0, 1, 2 are called integers. (Integer is a number representing the number of objects, and 0 means there are 0 objects. )

positive integer

Positive integer set symbol N* or N﹢.

Natural number = non-negative integer

Non-negative integer set (or natural number set), including 0 and positive integer, symbol n is a positive integer, and zero is a natural number. That is, all integers except negative integers.

Score:

Divide the unit "1" into several parts on average, and the number representing such a part or parts is called a fraction.