Prime number calculator

The prime number calculator will check if a number is prime or not and in each case will offer a step-by-step explanation. You also ave the opportunity to see a list of prime numbers up to 1 million (1000000). 

Why is 9 not prime?

9 has factors other than 1 and itself. Here's a detailed explanation:

• A prime number has exactly two factors: 1 and itself.
• 9 has the following factors: 1, 3, and 9.
• Since it has more than two factors, it cannot be prime.

The smallest factor (other than 1) is 3. You can divide 9 by 3 to get 3.

Remember: Any number that's not prime is called a composite number (except for 1, which is neither prime nor composite).

7 is prime because it can only be divided by 1 and 7

Sometimes, it is tricky to see if a number is prime or not. Try putting 93 in the calculator and you will see that 93 is not prime because it can be divided by 3 and 31.

However, 93 looks prime if you do not take time to think about.

Use the calculator below to practice until you have no problem recognizing what a prime number is.

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