159. Find the relationship between the prime numbers $p_{1}, q_{1}$, $p_{2}, q_{2}$, if it is known that the numbers $p_{1} q_{1}$ and $p_{2} q_{2}$ have the same sum of divisors.
159. Answer. $\left(p_{1}+1\right)\left(q_{1}+1\right)=\left(p_{2}+1\right)\left(q_{2}+1\right)$.