# Number and number system in English

By sonu

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 2and 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.