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).
Recall that a number is prime if it can only be divided by 1 and itself.
Why is 9 not prime?
9 has factors other than 1 and itself. Here's a detailed explanation:
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.