On $k$-layered numbers

Abstract

A positive integer $n$ is said to be $k$-layered if its divisors can be partitioned into $k$ sets with equal sum. In this paper, we start the systematic study of these class of numbers. In particular, we state some algorithms to find some even $k$-layered numbers $n$ such that $2^{\alpha}n$ is a $k$-layered number for every positive integer $\alpha$. We also find the smallest $k$-layered number for $1\leq k\leq 8$. Furthermore, we study when $n!$ is a $3$-layered and when is a $4$-layered number. Moreover, we classify all $4$-layered numbers of the form $n=p^{\alpha}q^{\beta}rt$, where $\alpha$, $1\leq \beta\leq 3$, $p$, $q$, $r$, and $t$ are two positive integers and four primes, respectively. In addition, in this paper, some other results concerning these numbers and their relationship with $k$-multiperfect numbers, near-perfect numbers, and superabundant numbers are discussed. Also, we find an upper bound for the differences of two consecutive $k$-layered numbers for every positive integer $1\leq k\leq 5$. Finally, by assuming the smallest $k$-layered number, we find an upper bound for the difference of two consecutive $k$-layered numbers.