Composite Number Lesson for Kids: Composite numbers are numbers with more than two factors. These are also known as composites. Composite numbers are the opposite of prime numbers, with only two factors: 1 and the number itself. Any natural number that isn't a prime number is composite because it can be divided by more than two numbers. For instance, 6 is a composite number because it can be divided by 1, 2, 3, and 6.
In this article, we will cover the definition of composite numbers, their properties, the smallest composite number, even and odd composite numbers, a list of composite numbers, and the difference between prime and composite numbers, along with many solved examples.
What are Composite Numbers in Maths?
Composite numbers are numbers that can be made by multiplying two positive integers and having at least one divisor other than 1 and themselves. These numbers always have more than two factors.
Did You Know?
Any even number greater than 2 is composite.
Is 0 a Composite Number?
Zero (0) is not considered a prime or a composite number because it does not have any factors.
Composite Numbers Examples
The examples of composite numbers are 8, 12, 18, 20, 27 etc, such that:
| Composite Number | Factors |
|---|---|
8 | 1, 2, 4, 8 |
12 | 1, 2, 3, 4, 6, 12 |
18 | 1, 2, 3, 6, 9, 18 |
20 | 1, 2, 4, 5, 10, 20 |
27 | 1, 3, 9, 27 |
In all the examples provided, composite numbers have more than two factors. We can find many composite numbers within a range of natural numbers, such as from 1 to 1000 or beyond. In the next section, we will explore a list of composite numbers.
Properties of Composite Numbers
The properties of composite numbers are quite easy to remember:
- More Than Two Factors: Composite numbers have more than two factors.
- Evenly Divisible: They are evenly divisible by their factors.
- Self-Factor: Each composite number is a factor of itself.
- Smallest Composite: The smallest composite number is 4.
- Prime Factors: Each composite number includes at least two prime numbers as its factors (e.g., 10 = 2 × 5, where 2 and 5 are prime numbers).
- Divisibility by Composites: Composite numbers can also be divisible by other composite numbers.
List of Composite Numbers From 1-100
Here are the composite numbers between 1 and 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. |
List of Composite Numbers 1 to 200
The positive integers with more than two factors are composite numbers. Here is a table listing the composite numbers between 1 and 200:
| 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. |
How to Find Composite Number?
In this section of the article, we will understand how to recognize if the number is composite or not.
How to Determine if a Number is Prime or Composite
Find All Factors: Identify all the factors of the positive integer.
Check Number of Factors:
- Prime Number: If the number has exactly two factors (1 and itself), it is a prime number.
- Composite Number: If the number has more than two factors, it is a composite number.
Example: Determine if 14 is a composite number.
Find the Factors:
14÷1 = 14
14÷2 = 7
14÷7 = 2
14÷14 = 1
List of Factors: The factors of 14 are 1, 2, 7, and 14.
Since 14 has more than two factors, it is a composite number.
Types of Composite Numbers
In mathematics, composite numbers can be categorized into two main types:
Odd Composite Numbers
Odd composite numbers are all odd integers that are not prime. Examples include:
- 9
- 15
- 21
- 25
- 27
- 31
Even Composite Numbers
Even composite numbers are even integers that are not prime. Examples include:
- 4
- 6
- 8
- 10
- 12
- 14
- 16
Smallest Composite Number
The smallest composite number is 4, as
- Number 1 is not a composite number because it has only one divisor (1 itself).
- Numbers 2 and 3 are prime because they have exactly two factors (1 and themselves). Hence, 2 and 3 are not composite.
However, the number 4 has more than two factors: 1, 2, and 4. This satisfies the condition for a composite number. After 4, the next composite number is 6, which has factors 1, 2, 3, and 6.
Summary
- Smallest Composite Number: 4
- Smallest Prime Number: 2
- Smallest Odd Composite Number: 9
- Smallest Two-Digit Composite Number: 10
Difference Between Prime and Composite Numbers
The difference between prime numbers and composite numbers are:
| 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 Factorization of Composite Numbers
Here is a table showing composite numbers between 1 and 50 along with their prime factorizations. You can see here how the composites are factorized in prime numbers:
| Composite Numbers | Prime Factorization |
|---|---|
| 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 | 2 × 2 × 11 |
| 45 | 3 × 3 × 5 |
| 46 | 2 × 23 |
| 48 | 2 × 2 × 2 × 2 × 3 |
| 49 | 7 × 7 |
| 50 | 2 × 5 × 5 |
Examples on Composite Numbers for Kids
Example 1: Find if 328 is a composite number.
Solution:
Factors of 328 are
1, 2, 4, 8, 41, 82, 164, 328.
Therefore, 328 is a composite number.
Example 2: What is the prime factorization of 60?
Solution:
Prime factorization of 60 is:
60 = 2 × 2 × 3 × 5.
Example 3: List out the composite numbers from the given set of number: 2, 4, 9, 11, 21, 31, 44, 53, 67, 88, 101, 108.
Solution:
Composite numbers are:
4, 9, 21, 44, 88, 108.
Example 4: Find the product of first 5 composite numbers.
Solution:
The first 5 composite numbers are 4, 6, 8, 9, 10.
Hence, the product of first 5 composite numbers
= 4 × 6 × 8 × 9 × 10
= 17280
Therefore, the product of first five composite numbers is 17280.
Practice Questions on Composite Numbers for Kids
Q1. List all the composite numbers between 20 and 30.
Q2. Is 85 a composite number? Explain your reasoning.
Q3. What are the prime factors of 99?
Q4. What is the sum of all factors of the composite number 18?
Q5. Find the composite numbers among the following set of numbers: 27, 34, 45, 49, 53.
Q6. From the numbers given, list all the composite numbers: 2, 3, 4, 5, 6, 8, 10
Q7. What is the sum of the composite numbers between 10 and 20?
Q8. Compare the following pairs of numbers and identify which one is a composite number:
- a) 13 or 22
- b) 19 or 20
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