Get base10 mantissa and exponent of real (eg Float64)

Technically you are right, but I am after a string which I can just cut off at some point and insert a decimal dot, so I am flexible.

The point of the exercise is for printing, into LaTeX. That is, I want to generate output like raw"$4.92 \cdot 10^{-3}$" and raw"$22.71 \cdot 10^{6}$" (engineering notation).