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