A Pen By
J Michael Palermo IV

` ````
// number to be evaluated if prime
var theNumber = 99;
// obtain true|false from isPrime method
var primeResult = isPrime(theNumber);
// write the results
document.write("<hr />Is " + theNumber + " a prime number: " + primeResult);
function isPrime(n) {
// single digit primes
var s = [2,3,5,7];
// last digit of primes > 10
var ld = [1,3,7,9];
// will potentially contain divisibles
var divs = [];
// if 1 is entered, not prime
if (n==1) {return false;}
// determine if a single digit prime
if (s.indexOf(n) > -1) {return true;}
// if the last digit is potentially prime...
if (ld.indexOf(n%10) > -1) {
// determine divisibles
divs = getDivisibles(n);
document.writeln(divs);
} else {
// here because number ended with 0,2,4,5,6,or 8
return false;
}
// if no divisbles, it is a prime number
return (divs.length == 0);
}// isPrime
function getDivisibles(n) {
// start with an index of 2
var i = 2;
// initialize an empty array
var divs = [];
// while the index*index is less than the number...
while (i*i<=n) {
// if index evenly divides into number...
if (n%i==0) {
// determine what index divides into number
var upper = n/i;
// add index
divs.push(i);
// if index == upper, don't add to array twice
if (upper>i) {divs.push(upper);}
}
i++;
}// while
// sort the array in ascending order
divs.sort(function(x,y){return x-y;});
return divs;
}// getDivisibles
```

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