Numbers

A number is a mathematical object used for counting, labeling and measurement. Numbers written in the form of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and so on are known as Hindu-Arabic numerals, and the numbers written in the form of I, II, III, IV, V, VI, VII, VIII, IX, X and so on are known as Roman numerals. The following are the fundamental number systems.

Natural number: This refers either to a member of the set of positive numerals 1, 2, 3, 4 ... or the set of non-negative numerals 0, 1, 2, 3, 4... And a set of natural numbers is denoted by N.

Integer: An integer is a number that can be written without a fractional or decimal component and is denoted by Z. It can be a positive number or a negative number. For example, 5, 12, –398 and –898 are Integers, whereas 9.75, 5½ and √2 are not Integers.

Prime number: A prime number is a positive integer, greater than 1 that can be divisible only by 1 and the number itself. For example an integer 5 can be divided by only by 1 and 5 without a remainder. Number 6 is not a prime number because 2 and 3 can divide it. The prime numbers list: 2, 3, 5, 7, 11, 13, 17, 19…

Composite number: A composite number is a positive integer that has at least one positive divisor other than one or itself. For example number 6 is a composite number because 2 and 3 other than 1 and 6 can divide it. The composite numbers list: 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22...

Rational number: It is a number that is expressed as a fraction with a numerator and a denominator. The fraction a/b represents ‘a’ parts of a whole divided into ‘b’ equal parts. The symbol is denoted by Q.

Real number: It is the limit of a convergence sequence of rational numbers and includes all the measuring numbers. They are usually represented with decimal points and is denoted by R.

Complex number: It is the combination of real and imaginary numbers and is denoted by C. It can be expressed as ‘a + bi’ or ‘a+ ib’, where ‘a’ and ‘b’ are real numbers.