PRIME NUMBERS & COMPOSITE NUMBERS

PRIME NUMBERS:

NUMBER	FACTORS	NO .OF FACTORS
1	1	1
2	1,2	2
3	1,3	2
4	1,2,4	3
5	1,5	2
6	1,2,3,6	4
7	1,7	2
8	1,2,4,8	4
9	1,3,9	3
10	1,2,5,10	4

👉 The numbers having only two factors 1 and itself are called prime numbers.

👉 From the above table we observe the numbers 2, 3,5and 7 having only two factors 1 and itself .

So 2, 3, 5 and 7 are prime numbers.

PRIME NUMBERS UP TO 100:

👉 There are 25 prime numbers up to 100

2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

COMPOSITE NUMBERS:

👉 The numbers having more than two factors are called composite numbers.

👉 From the above table we observe the numbers 4, 6, 8, 9 and 10 having more than two factors.

So 4, 6, 8, 9 and 10 are composite numbers.

COMPOSITE NUMBERS UP TO 100:

👉 There are 74 composite numbers up to 100

4 6 8 9 10 12 14 15 16 18 20 21 22 24 25 26 27 28 30 32 33 34 35 36 38 39 40 42 44 45 46 48 49 50 51 52 54 55 56 57 58 60 62 63 64 65 66 68 69 70 72 74 75 76 77 78 80 81 82 84 85 86 87 88 90 91 92 93 94 95 96 98 99 100

NOTE:

👉 1 is neither prime nor composite.

TWIN PRIMES:

👉 A pair of prime numbers that differ by 2 are called twin primes.

Ex: The prime numbers 5 and 7 differ by 2.

So 5 and 7 are called twin primes and it is represented by (5, 7)

Similarly (3,5) ,(5,7) , (11,13) …… are twin primes.

CO-PRIME NUMBERS:

👉 Two numbers are said to be co-primes if they do not have any common factor other than 1.

👉 Co-prime numbers are also called relatively prime numbers.

Ex: 6, 5

Factors of 6 = 1, 2, 3, 6

Factors of 5 = 1, 5

Common factors of 6 and 5 = 1

So 6 and 5 are co-primes.

NOTE:

👉 Two prime numbers are always co-prime.

👉 Two consecutive numbers are always co-prime.

👉 Two co-primes may or may not be prime numbers.

worksheet pdf given below

PRIME NUMBERS & COMPOSITE NUMBERS