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# Prime Numbers

- Prime number
- A prime number has exactly two different factors, 1 and itself.

- Example 1:
- 7 = 1 × 7. The number 7 is only divisible by 1 and itself 7, so the number 7 is a prime number.

- Example 2:
- 11 = 1 × 11. The number 11 is only divisible by 1 and itself 11, so the number 11 is a prime number.

- Example 3:
- 10 = 1 × 10, 10 = 2 × 5. Since the number 10 is divisible by 1, 2, 5, 10. So the number 10 is not a prime number.

- Note:
- A prime number has exactly 2 factors, 1 and itself, for example, 7 and 11 are prime numbers.
- Since 10 = 1 × 10 and 10 = 2 × 5, so 10 is a composite number, it has 4 factors. 10 is not a prime number.

What is a prime number? A prime number has exactly two different factors, 1 and itself. For example, 5 = 1 × 5. Since there are no other factors of 5, so 5 is a prime number.