CFLib.org – Common Function Library Project

Description:
Returns True if the specified number is a prime number. A prime number is a positive integer that has two postive integer factors (the number is evenly divisible by 1 and itself). Note that 1 is not a prime number.

Return Values:
Returns a Boolean value

Example:

<cfset mynum = 11>
<cfset mynum2 = 15>

<cfoutput>
Given mynum = #mynum#<br>
IsPrimeNumber returns #IsPrimeNumber(mynum)#<br>
Given mynum2 = #mynum2#<br>
IsPrimeNumber returns #IsPrimeNumber(mynum2)# 
</cfoutput>

Parameters:

Full UDF Source:

/**
 * Returns True if the specified number is a prime number.
 * Minor edits by Rob Brooks-Bilson (rbils@amkor.com).  Edit by Steve Ford (steve.ford@enline.com) to fix misidentification of 4 as a prime number.  Algorithm improved by Shakti Shrivastava (divine_shammer@yahoo.com) -check up to sqr root of integer.  Further refined by Sierra Bufe (sierra@brighterfusion.com).
 * 
 * @param inNum      Any integer greater than one that  you wish to test for prime. 
 * @return Returns a Boolean value 
 * @author Douglas Williams (klenzade@i-55.com) 
 * @version 1.2, November 21, 2001 
 */
function IsPrimeNumber(inNum)
{
  var i=0;
  if (inNum lt 2){
    return False;
    break;
  }
  for (i=2; i LTE (sqr(inNum)); i=i+1) {
    if (NOT inNum MOD i) {
      return False;
      break;
    }
  }
  return True;
}