__Number__

**Digit**: For calculation or counting we used some symbol , that are known as digit.

There are two kinds of digit: i) Significant digit and ii) Signifying the empty place.

**Significant digit**: 1 to 9 is significant digit ,

Signifying the empty place: 0 is the Signifying the empty place.

**Number:** Two or more digit form a number.

Here 135 is a number but 1,3,5 are digit.

Note That: Every digit is number but every number is not digit.

**Enumeration**: Any number written in digits is known as the enumeration.

**Natural Number**: The numbers except zero and positive integers are natural number.

**Intrinsic value**: The value of a digit used in a number depends on it s position in the number. A significant digit expressed separately is its intrinsic value.

Place value: When several digits are written side by to denote a number, each significant digit has a place value for its position.

** 5876**

Here 5876 forms number. Place value of 6 is ones and intrinsic value is 6

Place value of 7 is tens or, 70 and intrinsic value is 7

Place value of 8 is hundreds or, 800 and intrinsic value is 8

Place value of 5 is thousands or, 5000 and intrinsic value is 5.

Note: Place value will be changed but Intrinsic value not changed.

Even number: The number which are exactly divisible by 2are called even numbers. Such as 8,20,68,82 etc.

Odd number: The number which are not exactly divisible by 2are called odd numbers. Such as 5,7,15,21 etc.

**Key points:**

Even number+ Even number = Even number.

Even number+ Even number = Even number.

Even number+ Odd number = Odd number.

Even number- Even number = Even number.

Even number- Even number = Even number.

Odd number+ Odd number = Odd number.

Even number Even number = Even number.

Odd number Odd number = Odd number.

Even numberOdd number = Odd number.

**Prime number:** The number which is greater than 1 and has no factors other than one and the number itself, is called a prime number. Such as 2,3,5,7,11 etc.

The number of prime number from 1 to 100 is 25.

Summation of prime number from 1 to 100 is 1060.

Formula for prime number 4422322321

The number of prime number from 1 to 10=4

The number of prime number from 11 to 20=4

The number of prime number from 21 to 30=2

The number of prime number from 31 to 40=2

The number of prime number from 41 to50=3

The number of prime number from 51 to 60=2

The number of prime number from 61 to 70=2

The number of prime number from 71 to 80=3

The number of prime number from 81 to 90=2

The number of prime number from 91 to 100=1

If any number is not divisible by 2,3,5,7 then the number is prime number.

Prime numbers are from 1 to 100 is 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,51,53,59,61,67,71,73,79,83,89,97.

**Co-prime number:** Two or more numbers are called co-prime to each other if they have no common factor except 1.