Project Euler 179

Consecutive positive divisors

As we only need calculate the number of divisors for integers 1 < n < 10^7, It says possible to bruteforce whose running time is $O(n \times \sqrt{n})$. Of course this method is far from satisfy. My code runs in 0.869 seconds. The insights is that for every number n we have $n = p_1^{m_1} \times p_2^{m_2} \times … \times p_i^{m_i}$ and the number of factors of n is $m_1 \times m_2 \times … \times m_i$.