Fast Greatest Common Divisor (GCD) Algorithm

/// <summary>
/// Find the Greatest Common Divisor
/// </summary>
/// <param name="a">Number a</param>
/// <param name="b">Number b</param>
/// <returns>The greatest common Divisor</returns>
public static long GCD(long a, long b)
{
    while (b != 0)
    {
        long tmp = b;
        b = a % b;
        a = tmp;
    }

    return a;
}

/// <summary>
/// Find the Least Common Multiple
/// </summary>
/// <param name="a">Number a</param>
/// <param name="b">Number b</param>
/// <returns>The least common multiple</returns>
public static long LCM(long a, long b)
{
    return (a * b) / GCD(a,b);
}