In Mathematics, Composite numbers are the numbers which have more than two factors, unlike prime numbers which have only two factors, i.e. 1 and the number itself. These numbers are also called composites.
All the natural numbers which are not prime numbers are composite numbers as they can be divided by more than two numbers. For example, 6 is composite because it is divisible by 1, 2, 3 and even 6, such as:
- 6÷1 = 6
- 6÷2 = 3
- 6÷3 = 2
- 6÷6 = 1
Table of Contents:
- Definition
- Types
- List
- Smallest Composite Number
- Difference Between Prime and Composite Numbers
- Prime Factorisation
What is a Composite Number in Maths?
The integers which can be generated by multiplying the two smallest positive integers and contains at least one divisor other than number ‘1’ and itself is known as composite numbers. These numbers always have more than two factors.
Fact: Any even number which is greater than 2 is a composite number.
How to Determine the Composite Number?
The procedures to find whether a given number is prime or composite:
- Find all the factors of the positive integer
- A number is said to be prime if it has only two factors, 1 and itself.
- If the number has more than two factors, then it is a composite.
Example: Find if 14 is a composite number.
Let us find the factors of 14.
- 14÷1 = 14
- 14÷2 = 7
- 14÷7 = 2
- 14÷14 = 1
As we can see, the factors of 14 are 1,2,7 and 14, so it is a composite number.
List of Composite Numbers
The positive integers having more than two factors are composite numbers. The list of composite numbers up to 150 are:
| 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, 102, 104, 105, 106, 108, 110, 111, 112, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 128, 129, 130, 132, 133, 134, 135, 136, 138, 140, 141, 142, 143, 144, 145, 146, 147, 148, 150, 152, 154, 155, 156, 157, 158, 159, 160, 162, 164, 165, 166, 168, 170, 172, 174, 175, 176, 177, 178, 180, 182, 184, 185, 186, 187, 188, 189, 190, 192, 194, 195, 196, and 198. |
Is 0 a Composite Number?
Zero (0) is considered as neither prime nor a composite number because it do not have any factors.
Types of Composite Numbers
There are two main types of composite numbers in Maths are:
- Odd Composite Numbers or Composite Odd Numbers
- Even Composite Numbers or Composite Even Numbers
Odd Composite Numbers
All the odd integers which are not prime are odd composite numbers. Examples of composite odd numbers are 9, 15, 21, 25, 27, 31, etc.
Consider the numbers 1, 2, 3, 4, 9, 10, 11,12, and 15 . Here 9 and 15 are the odd composites because those two numbers have the odd divisors and satisfy the composite condition.
Even Composite Numbers
All the even integers which are not prime are even composite numbers. Examples of composite odd numbers are 4, 6, 8, 10, 12, 14, 16, etc.
Consider the numbers 1, 2, 3, 4, 9, 10, 11,12, and 15 again . Here 4, 10 and 12 are the even composites because those two numbers have the odd divisors and satisfy the composite condition.
Composite Numbers 1 to 100
Here is the list of composite numbers from 1 to 100 in Maths. Students can keep a note of this and also try to write the numbers beyond 100 for practice, such composites from 1 to 200 or till 500.
Smallest Composite Number
4 is the smallest composite number.
Why?
1 is not a composite number because the sole divisor of 1 is 1. The positive integers 2 and 3 are prime numbers because it can be divided by only two factors, one and itself. Hence 2 and 3 are not composite.
But in the case of number 4, we have more than two factors. The divisors of 4 are 1,2,4. So this number satisfies the condition of a composite number as mentioned above. After 4, 6 is the next composite positive integer, which has factors 1, 2, 3 and 6.
Hence, 4 is the smallest composite number (Proved).
Important Notes:
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Also, read:
Prime and Composite Numbers
The difference between the prime numbers and the composite numbers in Maths are listed below:
| Prime Numbers | Composite Numbers |
|---|---|
| It can only be divided by 1 and itself, thus have only two factors. | It has more than two factors(1 and itself). |
| It can only be written as a product of two numbers | It can be written as the product of two or more numbers |
| Example: 5 has factors are 1 and 5 | Example: 4 has factors are 1, 2 and 4 |
Prime Factorisation of Composite Numbers
The list of composite numerals from 1 to 50 are given here with their prime factorisation. You can see here how the composites are factorised in prime numbers. Check the below table to understand better. With the help of this table, you can also find the composites beyond 50 with their prime factorisation.
| Composite Numbers | Prime Factorisation |
| 4 | 2 × 2 |
| 6 | 2 × 3 |
| 8 | 2 × 2 × 2 |
| 9 | 3 × 3 |
| 10 | 2 × 5 |
| 12 | 2 × 2 × 3 |
| 14 | 2 × 7 |
| 15 | 3 × 5 |
| 16 | 2 × 2 × 2 × 2 |
| 18 | 2 × 3 × 3 |
| 20 | 2 × 2 × 5 |
| 21 | 3 × 7 |
| 22 | 2 × 11 |
| 24 | 2 × 2 × 2 × 3 |
| 25 | 5 × 5 |
| 26 | 2 × 13 |
| 27 | 3 × 3 × 3 |
| 28 | 2 × 2 × 7 |
| 30 | 2 × 3 × 5 |
| 32 | 2 × 2 × 2 × 2 × 2 |
| 33 | 3 × 11 |
| 34 | 2 × 17 |
| 35 | 5 × 7 |
| 36 | 2 × 2 × 3 × 3 |
| 38 | 2 × 19 |
| 39 | 3 × 13 |
| 40 | 2 × 2 × 2 × 5 |
| 42 | 2 × 3 × 7 |
| 44 | 4 × 11 |
| 45 | 3 × 3 × 5 |
| 46 | 2 × 23 |
| 48 | 2 × 2 × 2 × 2 × 3 |
| 49 | 7 × 7 |
| 50 | 2 × 5 × 5 |
To learn more about the different types of numbers, download BYJU’S -The Learning App from the Google play store and watch interactive videos.
Frequently Asked Questions – FAQs
What is a composite number?
Is 2 a composite number?
Is 9 a composite number?
What are the 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.
