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# Is 91 a Prime Number?

To know whether 91 is a prime number or not, it is important to factor it. To recall, a prime number is a whole number which can be divided only with 1 and itself i.e. it has only two factors. Now, is 91 a prime number?

## 91 is a Prime Number or Not?

First, the factors the number ninety one has to be found out. Check how to factor a number to learn more about finding factors of any number. Now, the factors of 91 using factorization will be as follows:

• Factors of 91 = 1, 91, 7, 13

It is seen that there are 4 factors of 91 which is greater than 1 and so, 91 does not satisfy the condition of prime numbers. Hence, 91 is not a prime number.

Check for Yourself: Prime Numbers Calculator

Let’s learn why 91 is not a prime number using a simple shortcut.

### Why is 91 not a Prime? (Shortcut)

To find whether 91 is a prime number, first, check whether (9+1) is divisible by 3. Since 9+1 is 10 which is not divisible by 3, continue with the following steps.

• Step 1: Take the square root of 91 i.e. √91 = 9.53
• Step 2: Choose prime numbers less than 9 and see if any of the numbers equally divides 91.
• Step 3: It can be seen that the number 7 divides 91 perfectly. So, 91 is divisible by 7 other than 1 and itself. Hence, it is not a prime number.

The detailed methods on how to find prime numbers are explained in this lesson along with a shortcut technique. Check this lesson to easily find whether a given number is a prime or not.

Now, one might get a doubt that what type of number is 91?

### So, 91 is a Composite Number?

The factors of 91 are already known which are 1, 7, 13, 91. As the total number of factors of 91 is more than 2, it satisfies the condition of composite numbers. Hence, 91 is a composite number.

### What Kind of Number is 91 then?

It is now already known that 91 does not fall under the classification of prime numbers. Some of the categories where 91 can be considered include:

• A natural number
• A positive integer
• An odd number
• A rational number
• A composite number
• A whole number