On multivariable averages of divisor functions

We deduce asymptotic formulas for the sums $\sum_{n_1,\ldots,n_r\le x} f(n_1\cdots n_r)$and$\sum_{n_1,\ldots,n_r\le x} f([n_1\cdots n_r])$,where$r\ge 2$isafixedinteger,$[n_1,\ldots,n_r]$ stands for the least common multiple of the integers $n_1,\dots ,n_r$ and $f$ is one of the divisor functions ${\tau }_{1,k}(n)$ ($k\ge 1$), ${\tau }^{(e)}(n)$ and ${\tau }^{\ast }(n)$. Our formulas refine and generalize a result of Lelechenko (2014). A new generalization of the Busche-Ramanujan identity is also pointed out.