# Class 6 Chapter 3 Playing with Numbers Math Formulas

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#### Some facts about Factors and Multiples:-

• Only 1 is a number which is a factor of every number.
• Every number is a factor of itself.
• All the factors of any number are the exact divisor of that number.
• All the factors are less than or equal to the given number.
• There are limited numbers of factors of any given number.
• All the multiples of any number are greater than or equal to the given number.
• There are infinite multiples of a given number.
• Every number is a multiple of itself.

Note:-

1 is neither prime nor composite.

2 is the only even number which is prime. It is the smallest prime number.

Divisibility:-

Divisibility by 1

Any number divided by 1 will give the same number back.

Divisibility by 2

All even number are divisible by two. The number ends with  2,4,6,8 including 0 are always completely divisible by 2.

Divisibility by 3

If the sum of the digits of a number is divisible by 3, the number is also divisible by 3.

Divisibility by 4

If the last two digits of a number are divisible by 4, then the number is also completely divisible by 4.

Divisibility by 5

All numbers which has last digit as 0 or 5 are always divisible by 5.

Divisibility by 6

All numbers which are divisible by both 2 and 3 are divisible by 6.

Divisibility by 8

If the last three digits of a number are divisible by 8, then the number is also completely divisible by 8.

Divisibility by 9

If the sum of digits of the number is divisible by 9, then the number is also divisible by 9.

Divisibility by 10

Any number whose last digit is 0, is divisible by 10.

Divisibility by 11

If the difference of the sum of alternative digits of a number is divisible by 11 then the number is completely divisible by 11.