Extract multiplier from siunitx prefix

Question

Is there a way to extract the multiplication factor that each siunitx prefix represents. Basically, can I automate ExplainPrefix to correctly produce the correct output. Current output uses x as the exponent:

MWE:

\documentclass{article}
\usepackage{siunitx}
\usepackage{expl3}
%% http://tex.stackexchange.com/questions/100542/how-to-extract-the-name-of-a-macro
\ExplSyntaxOn
\newcommand{\CsToStr}[1]{\cs_to_str:N #1}
\ExplSyntaxOff
\newcommand{\ExplainPrefix}[1]{%
\par
The prefix \CsToStr{#1} (symbol: \si{#1}) representes multiplication by $10^x$.
}%
\DeclareSIPrefix\wacky{X}{41}
\begin{document}
\ExplainPrefix{\kilo}
\ExplainPrefix{\micro}
\ExplainPrefix{\wacky}
\end{document}

Answer 1

You are looking for

\si[prefixes-as-symbols = false]{#1}

which will convert the prefix symbol to the value (a single stand-alone prefix is allowed here: I plan in figure to introduce some kind of 'no-op' unit to make the logic a bit easier).

The data for this conversion is stored in the internal property list \l__siunitx_prefix_forward_prop, which may of course change in the future but is there if you want to do something more complex.