Largest prime factor

by Daniel Lamb

HTML

<h1 id="answer"></h1>

JavaScript

function smallestFactor(n) {
    var end = Math.floor(Math.sqrt(n));
    for (var i = 3; i <= end; i += 2) {
        if (n % i == 0) return i;
    }
    return n;
}

function primeFactorList(n) {
    var largest = 0;
    while (n != 1) {
        var factor = smallestFactor(n);
        if (factor > largest) largest = factor;
        n /= factor;
    }
    return factor;
}
document.getElementById('answer').innerHTML = primeFactorList(600851475143);