Lists prime factors of a given natural integer, from greatest to smallest
    :param n: Natural integer
    :rtype : list of all prime factors of the given natural n

def prime_factors(n):
    """Lists prime factors of a given natural integer, from greatest to smallest
    :param n: Natural integer
    :rtype : list of all prime factors of the given natural n
    """
    i = 2
    while i <= sqrt(n):
        if n % i == 0:
            l = prime_factors(n/i)
            l.append(i)
            return l
        i += 1
    return [n]