## IsPrime

**Posted On **2011-12-31 by FortyPoundHead

**Keywords:** ASP VBScript Math Functions

**Tags:** ASP Scripting VBScript Windows

**Views:** 2046

This handy little vbscript function checks to see if a number is a primary number.

Prime numbers are commonly found in encryption schemes that use Public/Private keys.

Pass it a number, and it will return a true/false value depending on the "primeness" of the number.

It first assumes that the number passed is false. Then it simply checks if it is less than 2, divisible by two, or has a square.

If it makes it past those checks, then it must be prime. The value is set and returned to the caller.`'**************************************`

' Name: IsPrime

' Description:Checks to see if a number is a primary number. Prime numbers are commonly found in encryption schemes that use Public/Private keys.

'**************************************

function IsPrime(ByRef pLngNumber)

Dim lLngSquare

Dim lLngIndex

IsPrime = False

if pLngNumber < 2 Then Exit function

if pLngNumber Mod 2 = 0 Then Exit function

lLngSquare = Sqr(pLngNumber)

For lLngIndex = 3 To lLngSquare Step 2

if pLngNumber Mod lLngIndex = 0 Then Exit function

Next

IsPrime = True

End function

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