Which of the following statements is not correct?

Options

A. All prime numbers are odd numbers
B. There are infinitely many prime numbers
C. A prime has only two factors .
D. There are only four single digit prime numbers .

Answer

To determine which of the given statements is not correct regarding prime numbers, we will analyze each option one by one.

### Step-by-Step Solution:

1. **Understanding Prime Numbers**:
- A prime number is defined as a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. In other words, a prime number has exactly two distinct positive divisors: 1 and itself.

2. **Examine Each Option**:
- **Option A**: "All prime numbers are odd numbers."
- This statement is incorrect because the number 2 is a prime number and it is even. Therefore, not all prime numbers are odd.

- **Option B**: "There are infinitely many prime numbers."
- This statement is correct. It is a well-known mathematical fact that there are infinitely many prime numbers.

- **Option C**: "A prime number has only two factors."
- This statement is correct. By definition, a prime number has exactly two factors: 1 and the number itself.

- **Option D**: "There are only four single-digit prime numbers."
- This statement is correct. The single-digit prime numbers are 2, 3, 5, and 7, making a total of four.

3. **Conclusion**:
- After analyzing all the options, we find that **Option A** is the only statement that is not correct.

### Final Answer:
The statement that is not correct is **Option A: "All prime numbers are odd numbers."**

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