A prime number is a whole number greater than 1 that has exactly two factors:
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1
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The number itself
Examples of prime numbers
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2 → factors: 1, 2
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3 → factors: 1, 3
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5 → factors: 1, 5
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7 → factors: 1, 7
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11 → factors: 1, 11
✅ These numbers cannot be divided evenly by any other number.
Special case: The number 2
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2 is the smallest prime number
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The only even prime number
All other even numbers have more than two factors, so they are composite.
What are Composite Numbers?
A composite number is a whole number greater than 1 that has more than two factors.
Examples of composite numbers
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4 → factors: 1, 2, 4
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6 → factors: 1, 2, 3, 6
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8 → factors: 1, 2, 4, 8
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12 → factors: 1, 2, 3, 4, 6, 12
✅ Composite numbers can be written as a product of smaller numbers.
What about the number 1?
⚠️ 1 is neither prime nor composite
Why?
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It has only one factor (1)
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Prime numbers need two factors
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Composite numbers need more than two factors
Key differences: Prime vs Composite
| Prime Numbers | Composite Numbers |
|---|---|
| Exactly 2 factors | More than 2 factors |
| Cannot be factored further | Can be factored |
| Examples: 2, 3, 5, 7 | Examples: 4, 6, 8, 9 |
How to tell if a number is prime or composite
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Count how many numbers divide it evenly.
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If only 1 and itself → Prime
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If more than two → Composite