Prime Number and Composite Number
Find out if a number is prime number or composite number
You can input a number and find if it is a prime number or composite number and the factors for the number.
What are Prime and Composite Numbers?
Prime Number Definition
Prime numbers are positive numbers that can only divisible by itself or by 1.In other words, the number which has exactly two factors 1 and the number itself is said to be a Prime number.
2 is a even prime numberPrime numbers 1 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 Number Definition
Composite Numbers are positive numbers that has more than two factors.In other words which can be written as multiplication of two or three numbers.
Example of Composite Numbers from 1 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.
How to find if a number is prime number?
First method :
Step 1
Divide the number by smaller prime numbers 2 , 3, 5 and so on..If we get a whole number then it cant be a prime number.
Step 2
If we dont get the whole number as a result of dividing the number by prime numbers, then it is prime number.
Example:
Check 8 is a prime or not.
Divide 8 by 2 we get a result 4 and that is whole number so it fails to be a prime number.Check 7 is a prime or not.
Divide 7 by 2 we dont get whole number as result , repeat the process of dviding the number by next prime number 3 and still we dont get whole number as result again repeat by dividing 7 by 5 still it gives non whole number.since there is no factor before 7 we can conclude that 7 is a prime
Second method :
Step 1
Find all factors of the number
Step 2
If the number has only two factors, then it is a prime otherwise it is composite number.
Example:
Check 6 is a prime or not.
Factors of six are 1, 2, 3 and 6.
Since it has factors more than two it is not a prime number.
What is Twin Prime?
Definition of Twin Prime:
Two prime numbers are said to twin prime if their difference is exactly two.
Example:
(3,5) , (5,7) , (11,13) and so on..
Is (2,3) a twin prime?
No, because two is a only even prime and their difference is not exactly two.
Table of Numbers - Is It Prime or Composite Number?
| Input | Prime number or Composite number | Reason |
|---|---|---|
| 0 | Neither Prime nor Composite | Prime number has to be greater than 1. |
| 1 | 1 is not a prime number | It has only one factor |
| 2 | 2 is an even prime number | It has only two factors 1 and 2 itself. |
| 3 | 3 is a prime number | It has only two factors 1 and 3 itself. |
| 4 | 4 is a composite number | It has more than two factors.Factors are 1,2 4 |
| 5 | 5 is a prime number | It has only two factors. |
| 6 | 6 is a composite number | It has 1,2,3,6 factors |
| 7 | 7 is a prime number | it has only two factors 1 and itself |
| 8 | 8 is a composite number | It has 1, 2, 4,8 as the factors |
| 9 | 9 is a composite number | 9 is divisible by 3.So it is not a prime |
| 10 | 10 is a composite number | 10 is divisible by 5 |
| 11 | 11 is a prime number | 11 has no factors rather than 1 and 11 |
| 12 | 12 is a composite number | 12 is divisible by 2 , 3 , 4 and 6 which is other than 1 and 12 |
| 13 | 13 is a prime number | 13 has only two factors |
| 14 | 14 is a composite number | 14 is divisible by 2 and 7 |
| 15 | 15 is a composite number | 15 = 3 x 5 and so it is composite number |
| 16 | 16 is a composite number | 16 = 2 x 8 it is a composite number |
| 17 | 17 is a prime number | It has only two factors |
| 18 | 18 is a composite number | 18 can be written as multiplication of two number. |
| 19 | 19 is a prime number | It has only two factors |
| 20 | 20 is a composite number | 20 can be written as 4 x 5 |
| 21 | 21 is a composite number | 21 has 3 and 7 as factors rather than 1 and 21 itself |
| 23 | 23 is a prime number | It has only two factors. |
| 25 | 25 is a composite number | 25 is a square of 5. |
| 26 | 26 is a composite number | It has 13 and 2 as a factor |
| 27 | 27 is a composite number | 27 = 3 x 9 can be written as multiplication of two number. |
| 29 | 29 is a prime number | It has only two factors |
| 31 | 31 is a prime number | It has only two factors |
| 32 | 32 is a composite number | 32 = 8 x 4 written as multiplication of two numbers |
| 33 | 33 is a composite number | factors are 11 and 3 rather than 1 and itself |
| 34 | 34 is a composite number | It has more than two factors |
| 36 | 36 is a composite number | It has more than two factors |
| 37 | 37 is a prime number | It has only two factors |
| 39 | 39 is a composite number | It has more than two factors |
| 41 | 41 is a prime number | It has only two factors |
| 43 | 43 is a prime number | It has only two factors |
| 47 | 47 is a prime number | It has only two factors |
| 51 | 51 is a composite number | It has more than two factors |
| 57 | 57 is a composite number | It has more than two factors |
| 59 | 59 is a prime number | It has only two factors |
| 61 | 61 is a prime number | It has only two factors |
| 67 | 67 is a prime number | It has only two factors |
| 73 | 73 is a prime number | It has only two factors |
| 75 | 75 is a composite number | It has more than two factors |
| 79 | 79 is a prime number | It has only two factors |
| 83 | 83 is a prime number | It has only two factors |
| 87 | 87 is a composite number | 3 and 29 are two factors |
| 89 | 89 is a prime number | It has only two factors |
| 93 | 93 is a composite number | 93 can written as 21 x 3 |
| 97 | 97 is a prime number | It has only two factors |
| 99 | 99 is a composite number | It has more than two factors |
| 101 | 101 is a prime number | It has only two factors |
| 103 | 103 is a prime number | It has only two factors |
| 109 | 109 is a prime number | It has only two factors |
| 111 | 111 is a composite number | 111 = 37 x 3 |
| 119 | 119 is a composite number | 119 = 17 x 7 |
| 123 | 123 is a composite number | 3 is one of the factor |
| 127 | 127 is a prime number | It has only two factors |
| 131 | 131 is a prime number | It has only two factors |
| 143 | 143 is a composite number | It has 11 as a factors |
| 149 | 149 is a prime number | It has only two factors |
| 599 | 599 is a prime number | It has only two factors |
| 601 | 601 is a prime number | It has only two factors |
| 610 | 610 is a composite number | It has more than two factors |
| 1325 | 1325 is a composite number | It has more than two factors |
| 1999 | 1999 is a prime number | It has only two factors |
| 2001 | 2001 is a composite number | It has 3 as a factors |
| 2027 | 2027 is a prime number | It has only two factors |
| 9973 | 9973 is a prime number | It has only two factors |
| 9999 | 9999 is a composite number | 9 and 11 are the factors rather than 1 and 9999 |
Frequently Asked Questions on Prime Number and Composite Number
Number 2 is the first and lowest prime number.
And it is also known as even prime.
The largest known prime number (as of May 2022) is 2 to the power of 82,589,933 − 1, a number which has 24,862,048 digits when written in base 10.
According to Euclid's theorem there are infinitely many prime numbers, so there is no largest prime.
2 is the only even prime number
No, 1 is neither a prime nor a composite number.
No, 0 is not a prime nor a composite number.
Because 0 is considered to be a neutral number.
A number to be a prime it has to be greater than 1 and so 0 is not.
