Introduction

 A number is defined as an arithmetical value.

Types of Numbers

  • Prime numbers
  • Even numbers
  • Odd numbers
  • Whole numbers
  • Natural numbers
  • Composite numbers

Perfect number: Perfect number is a number in which sum of all the factors of the number is equal to twice the number.

For example: 28 is a perfect number because all the factors of 28 are 1,2,4,7,14 and 28 whose sum  = {\rm{ }}1{\rm{ }} + {\rm{ }}2{\rm{ }} + {\rm{ }}4{\rm{ }} + {\rm{ }}7{\rm{ }} + {\rm{ }}14{\rm{ }} + {\rm{ }}28{\rm{ }} = {\rm{ }}56{\rm{ }} = {\rm{ }}2{\rm{ }} \times {\rm{ }}28 , whereas 10 is not a perfect number because all the factors of 10 are 1, 2, 5 and 10 whose sum  = {\rm{ }}1{\rm{ }} + {\rm{ }}2{\rm{ }} + {\rm{ }}5{\rm{ }} + {\rm{ }}10{\rm{ }} = {\rm{ }}18{\rm{ }} \ne {\rm{ }}2{\rm{ }} \times {\rm{ }}10.

Even number: A number which is divisible by 2 is called an even number.
For example: 2, 4, 6, 8, 10….

Odd number: A number which is not divisible by 2 is called an odd number.
For example: 1, 3, 5, 7, 9, …

A number with 0, 2, 4, 6, 8 at the unit’s place is an even number.
So, 250, 2732, 29354, 34596 are even numbers.
Obviously, the numbers 257, 3249, 7321 are odd numbers.

  • 2 is the smallest prime number which is even.
  • Every prime number except 2 is odd.
  • In this chapter, we will also learn about HCF, LCM, prime factorization, and their properties in detail.
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