In mathematics, a 'number system' is a set of numbers (in the broadest sense of the word), together with one or more operations, such as addition or multiplication.setnumbersadditionmultiplication Examples of number systems include: natural numbers, integers, rational numbers, algebraic numbers, real numbers, complex numbers and prime numbersnatural numbersintegersrational numbersalgebraic numbersreal numberscomplex numbers

All digits are numbers but all numbers are not digit. Two or more digit makes a number.

The positive (+) integer which are used for counting and ordering is called natural numbers. It is denoted by N or. For example, N= {1, 2, 3, 4 ………….. } Properties:  Natural numbers start from 1.  There is no highest number in natural number. i.e.;  The addition and multiplication of two natural numbers is also natural a number.  The subtraction and division of two natural numbers may be natural number or not may be.

The number which is divisible by 1 and itself only is called prime number. For example: 2, 3, 5, 7, 11, 13 …  Write down the difference between the highest and lowest prime numbers which are lies 18-44? Solution: The prime number which are lies is = 19,23,29,31,37,41,43 Here, the highest prime number is = 43 and the lowest prime number is = 19 Therefore, the difference is = = 24

The number which is divisible not only by 1 and itself but also other numbers is called Composite number. For example, 4, 6, 8, 10, 12…

 Those natural numbers are divisible by 2 is called even number. It is denoted by 2N. For example, {2, 4, 6, 8, 10…}  Those natural numbers are not divisible by 2 is called odd number. It is denoted by (2N+1). For example, {3, 5, 7, 9, 11…}

 The number which can be expressed in the form where p is any integer and q is an integer but not equal to zero is called a rational number. To state it formally The set Q={……,-5,-4,-2,0,3/7,5/8,2,7…..}. For examples, 3 = 3/1, -7 = -7/1 … Rational numbers can be represented by decimals. The decimal of some fractions are terminating or finite. For examples, ½=0.5, 2/5= 0.4 and 2/8= 0.25 etc. The decimal of some fractions are non terminating or infinite but repeating. For example, 1/3= … = 0.3, 5/11= … = 0.45 etc.

 The numbers which cannot be expressed in the form, where and p, q are both integers, are called irrational numbers. For examples: are irrational numbers.  The decimals irrational numbers are non- terminating and non-repeating. For example, …., …..etc are irrational numbers.