Prime numbers
2, 3, 5 and 7 are prime because each has exactly two factors.
Prime numbers are greater than 1.
Year 5
Know and use the vocabulary of prime numbers, prime factors and composite numbers
Classify numbers as prime or composite and use related number vocabulary accurately.
Lesson overview
Number - multiplication and division
A prime number has exactly two factors: 1 and itself. A composite number has more than two factors. Prime factors are the prime numbers that multiply together to make a number.
Composite numbers
12 is composite because it has many factors.
1, 2, 3, 4, 6, 12
more than two factors
Composite numbers can be made from smaller factors in several ways.
Prime factors
12 can be built from 2 x 2 x 3.
Prime factors are the prime numbers inside a number.
Worked example
Is 29 prime or composite?
- Check whether 29 is divisible by smaller whole numbers.
- It is not divisible by 2, 3 or 5.
- It has no factors other than 1 and 29.
- So 29 is prime.
Round 1: Learn it
Use the factor rules carefully when deciding whether a number is prime or composite.
Finish this round to unlock Round 2: Show you know it.
Question 1
Which number is prime?
Question 2
Which number is composite?
2 factors
2 factors
more than 2 factors
Question 3
Which prime factors make 12?
Question 4
Is 1 prime or composite?
only one factor
Question 5
Which number has exactly two factors?
Common mistakes
Watch for these as you work through the lesson.
- Calling 1 a prime number.
- Mixing up prime numbers and prime factors.
- Forgetting to test whether a number has another factor.
Related topics
These ideas connect closely to this lesson.
- Identify multiples and factors, including finding all factor pairs of a number, and common factors of two numbers.
- Solve problems involving multiplication and division, including scaling and correspondence problems.