Example 1 · level 1
Which of these numbers is prime?
- 15
- 25
- 23
- 27
Show solution
- 23 has factors 1, 23, so it is prime.
Answer: 23
CLASS 5 MATHS · FACTORS AND MULTIPLES
Prime and composite numbers
A prime number has exactly two factors: 1 and itself. 1 is neither prime nor composite.
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Worked examples
Example 2 · level 2
Which of these numbers is composite?
- 15
- 37
- 13
- 19
Show solution
- 15 has factors 1, 3, 5, 15, so it is composite.
Answer: 15
Example 3 · level 3
Which of these numbers is composite?
- 89
- 47
- 71
- 35
Show solution
- 35 has factors 1, 5, 7, 35, so it is composite.
Answer: 35