product-units mode with siunitx package

Question

I am trying to combine two or more values with one SI comment. For example, I would like to write 2 x 5 mL instead of 2 mL x 5 mL. I guess and as I saw before: How can I manage to get something like that?

\documentclass[pagesize=pdftex, paper=a4, parskip, fontsize=12pt, toc=bibnumbered, captions=tableheading, captions=nooneline, BCOR=5mm, headsepline]{scrbook}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[ngerman, english]{babel}
\usepackage{amsmath}
\usepackage{upgreek}
\usepackage[version=4]{mhchem}
\usepackage{textcomp}
\usepackage{siunitx}
\sisetup{separate-uncertainty-units=repeat,use-xspace=true, sticky-per=true, range-units=single, range-phrase={\,--\,}, list-units=single, per-mode=power-positive-first, multi-part-units=single, product-units=single} 
%a few other packages 
\begin{document}
I would like to write "\verb|\SI{2x5}{\milli\L}|" to express 2 x 2 mL\\
but the only comment what works so far is:\\
"\verb|\SI{2}{\milli\L}\times\SI{5}{\milli\L}|" but only if you write it in $\SI{2}{\milli\L}\times\SI{5}{\milli\L}$ and you will get 2 mL x 5 mL.  


\end{document}```

Answer 1

Using \qtyproduct in combination with product-units=single, which you already used in your preamble, you end up with the following output:

\documentclass{scrbook}
\usepackage{siunitx}
\sisetup{product-units=single} 

\begin{document}
\qtyproduct{2 x 5}{\mL} 
\end{document}

Answer 2

I suggest you use the parse-numbers=false option:

\SI[parse-numbers=false]{2\times5}{\milli\L}

If you happen to use a newer version of the siunitx package -- i.e., a version that's more recent than spring 2021 -- you could also write, as @leandriis has suggested,

\qtyproduct{2 x 5}{\mL}

Note that with the newer version, \SI is deprecated and should be replaced with \qty.