How much is eine million mark dated 1923 worth?

I would say go to an appraiser but, in my humble opinion, so many of those were made, that they are a novelty item and nothing more. Thy are hardly worth the paper they were made from. The Weimar Republic was established in Germany following WWI. It was unable to control the economy due to a combination of ineptitude and heavy financial penalties imposed by the Allies. The result was about 3 years of hyperinflation during which the Weimar government printed ever-larger bills in a futile effort to keep up with exponential price increases. At the worst point in late 1923 the mark fell to approximately one 400-billionth of its 1920 value! Today most hyperinflation notes are just curiosities. So many were printed and became nearly worthless within a few days that most never circulated enough to become worn, and they're available for just a couple of dollars.

Sammler.com, a major German collectibles site quotes 1-million mark notes at €1, or about $1.40, in circulated condition. Uncirculated values depend on the bill's date: ones dated July 25 (25 Juli) sell for about twice that, while those dated August 9 go for about $15.