## How to check if the number is prime number in Excel?

As we all known, a prime number is a natural number which contains only two distinct natural number divisors: One and itself. If you have a list of numbers in a worksheet, how could you check if the numbers are prime numbers?

**Check if a number is prime number with array formula**

**Check if a number is prime number with User Defined Function**

#### ** Check if a number is prime number with array formula**

The following formula can help you identify the number whether it is a prime number or not, please do as this:

**1**. Enter the following formula into a blank cell – C2 for example beside your data:

**=IF(A2=2,"Prime",IF(AND(MOD(A2,ROW(INDIRECT("2:"&ROUNDUP(SQRT(A2),0))))<>0),"Prime","Not Prime"))** (* A2* is the cell contains the number that you want to check), and then press

**Ctrl + Shift + Enter**keys together, and you will get the result, if the number is prime, it will display “Prime” in the cell, if not, “Not Prime” will be displayed, see screenshot:

**2**. Then select the cell C2, and drag the fill handle down to the cells which you want to apply this formula, and all the numbers will be identified if is prime number or not. See screenshot:

#### ** Check if a number is prime number with User Defined Function**

The following **User Defined Function** also can help you to check the numbers if prime or not, please do as follows:

**1**. Hold down the **ALT + F11** keys to open the **Microsoft Visual Basic for Applications** window.

**2**. Click **Insert** > **Module**, and paste the following code in the **Module Window**.

**VBA code: Check if a number is prime or not:**

Function CheckPrime(Numb As Single) As Boolean 'Updateby Extendoffice 20160614 Dim X As Long If Numb < 2 Or (Numb <> 2 And Numb Mod 2 = 0) _ Or Numb <> Int(Numb) Then Exit Function For X = 3 To Sqr(Numb) Step 2 If Numb Mod X = 0 Then Exit Function Next CheckPrime = True End Function

**3**. Then save and close this code, go back to the worksheet, and enter this formula: **=checkprime(A2)** into a blank cell beside your number list, and then drag the fill handle down to the cells which you want to contain this formula, if the number is prime number, it will display TRUE, if not, it will display FALSE, see screenshot:

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