**Even number**– The number which is** divisible by 2 **and also ends with 0,2,4,6 and 8 is known as an even number. For example 20 ,82, 94, 106, 2008,

**Odd number**– The number which is **not divisible by 2**and also ends with 1,3, 5, 7, 9 is known as an **odd number. **For example – 11, 33, 555, 777, 9999 etc.,

**Natural number**– The number which is started from 1 and also counting numbers are known as a **natural number**. For example- 1,2, 3 …..

**Digit – 0,1,2, 3, 4, 5, 6, 7, 8, 9, these are known as digit.**

**Whole number **– The number which is started from zero is known as the **whole number. **For example – 0, 2, 3 …..

**Prime number**– The number having only two factors 1 and itself is known as a **prime number. **For example – 2 have only two factors like 1 and 2 itself.

**Composite number – **The numbers having more than two factors are known as composite numbers. For example- 4, 6, 8, 9, 10 etc.,

**Integer – **All counting numbers with negative and positive signs are known as **integers**. For example – -1, -2, -3, -4 … and 1, 2, 3, 4, …

**Co – prime number **– Two natural numbers whose HCF is 1, these numbers are known as **co-prime numbers**. For example – (4,9), (2,7)

**Rational number **– The number which is a form of p/q where p is not equal to zero and which is non-repeating is called a rational number. For example 2/3, 4/5,

**Place Value **– Any number in which other number forms again from any number that number is known as place value.

**Face Value** – The face value of a number is the digit of the face value itself.

**The largest one digit is 9**

**The largest two digits number is 99.**

**The largest three digits number is 999.**

**The largest four digits number is 9999.**

**The smallest 1 digit number is 1.**

**The smallest two digits number is 10.**

**The smallest three digits number is 1000.**

**The sum of n natural numbers is **n(n+1)/2**.**

**The sum of squares of n natural numbers is **n(n+1)(2n+1)/6**.**