largest_prime_factor.rb

# With help from: http://math.stackexchange.com/questions/389675/largest-prime-factor-of-600851475143

def largest_prime_factor(number)
    divisor = 2
    largest_divisor = 0
    until number == 1
        if number % divisor == 0
            number /= divisor
            largest_divisor = divisor
        else
            divisor += 1
        end
    end
    largest_divisor
end