Question 154
Find all pairs $(n, k)$ of positive integers such that
$$
\sigma(n) \phi(n) = \frac{n^{2}}{k}
$$
$$
\sigma(n) \phi(n) = \frac{n^{2}}{k}
$$
MathNet 2007-part-03 — 185 problems (EN–VI) Question 154
Math Olympiad Vault · MathNet 2007-part-03 — 185 problems (EN–VI)