Números superabundantes

Um número ${\displaystyle n}$ é dito superabundante se ${\displaystyle {\frac {\sigma (d)}{d}}<{\frac {\sigma (n)}{n}}}$ para qualquer ${\displaystyle d<n}$, onde ${\displaystyle \sigma (n)}$ representa a soma dos divisores de ${\displaystyle n}$

• Akbary, Amir; Friggstad, Zachary (2009), «Superabundant numbers and the Riemann hypothesis», American Mathematical Monthly, 116 (3): 273–275, doi:10.4169/193009709X470128 .
• Alaoglu, Leonidas; Erdős, Paul (1944), «On highly composite and similar numbers», American Mathematical Society, Transactions of the American Mathematical Society, 56 (3): 448–469, JSTOR 1990319, doi:10.2307/1990319 .