Class 6 Chapter 3: Playing with Numbers

# Class 6 Chapter 3: Playing with Numbers

Important Concepts and Formulas

1.      The factor of a given number divides the number exactly.

2.      Every number greater than 1 has at least two factors.

3.      A multiple of a number is the product of that number by any other whole number.

4.      Every number has infinite number of multiples.

5.      Every number is its smallest multiple.

6.      Every number other than 1, whose only factors are 1 and the number itself is called a prime number.

7.      Every number having more than two distinct factors is called a composite number.

8.      The number 1 is neither a prime nor a composite number.

9.      The only even prime number is 2, all other prime numbers are odd numbers.

10. There are 25 prime numbers between 1 and 100.

11. All the multiples of 2 are called even numbers.

12. The numbers which are not multiples of 2 are called odd numbers.

13. A number is completely divisible by 2 if it ends with 0, 2, 4, 6 or 8.

14. A number is completely divisible by 3 if the sum of its digits is a multiple of 3.

15. If a number is divisible by both 2 and 3, then it is divisible by 6.

16. A number is completely divisible by 4 if the number formed by its last two digits is divisible by 4.

17. A number is divisible by 5 if it has 0 or 5 in its ones place.

18. If the sum of digits of a number is a multiple of 9, then the number is divisible by 9.

19. A number is divisible by 10 if it has 0 in its ones place.

20. A number is completely divisible by 8 if the number formed by its last three digits is divisible by 8.