Composite Numbers
Numbers greater than 1 with more than two factors.
Key idea
Numbers greater than 1 with more than two factors.
In depth
A composite number has more than two factors, so it can be broken into smaller factors. Every whole number above 1 is either prime or composite.
Worked example
15 is composite: 15 = 3 × 5, and its factors are 1, 3, 5, 15.
Real-world uses
- Identifying numbers that can be built into rectangles or arrays in design and packaging
Common mistake
Assuming odd numbers are prime. 9, 15, 21 are odd and composite.
How to learn this
- Read the key idea and say it in your own words.
- Work through the worked example, then try a similar problem.
- Use the interactive lesson’s visual and mini-quiz to check the pattern.
Frequently asked questions
What is Composite Numbers?
Numbers greater than 1 with more than two factors. It is a topic at the intermediate level in Arithmetic & Number Sense.
Where is Composite Numbers used in real life?
Real-world examples: Identifying numbers that can be built into rectangles or arrays in design and packaging.
What should I learn before Composite Numbers?
Make sure you are comfortable with Prime Numbers, the previous topic in Arithmetic & Number Sense.
What is a common mistake with Composite Numbers?
Assuming odd numbers are prime. 9, 15, 21 are odd and composite.
How can I practise Composite Numbers?
Open the interactive lesson, play with the visual, then answer the three-question mini-quiz. Getting two right marks the topic complete.
What comes after Composite Numbers?
Move on to Prime Factorization next.
Related intermediate topics in Arithmetic & Number Sense
- Long Multiplication – Multiply by each digit of the multiplier, shift by place value, then add partial products.
- Long Division – Divide, multiply, subtract and bring down repeatedly to get the quotient.
- Factors and Multiples – Factors divide a number exactly; multiples are its products with whole numbers.
- Divisibility Rules – Quick tests: by 2 last digit even, by 3 digit-sum divisible by 3, by 5 ends 0/5, by 9 digit-sum divisible by 9.
- Prime Numbers – A prime has exactly two positive divisors: 1 and itself.
- Prime Factorization – Every integer above 1 is a unique product of primes.