Odd Multiperfect Numbers

Abstract

A natural number $n$ is called {\it multiperfect} or {\it$k$-perfect} for integer $k\ge2$ if $\sigma(n)=kn$, where $\sigma(n)$ is the sum of the positive divisors of $n$. In this paper, we establish the structure theorem of odd multiperfect numbers analogous as Euler's theorem on odd perfect numbers. We prove the divisibility of the Euler part of odd multiperfect numbers and characterize the forms of odd perfect numbers $n=\pi^\alpha M^2$ such that $\pi\equiv\alpha(\text{mod}8)$. We also present some examples to show the nonexistence of odd perfect numbers as applications.