I am not certain, but I think that seven Royales were built and that six survive.
Only 6 Royale were built by Bugatti, the 7th "Esders Roadster" is a replica built by Schlumpf brothers in the sixties with a stock of parts bought to Bugatti in 1963, the engine was provided by a train (autorail) as Bugatti was also a train manufacturer. This Replica is exposed at the entrance of the Musée at Mulhouse wich contains also 2 Royale in the main building.
FyI - The french MOG 2008 and 2017 were organized in Alsace and the "soirée de gala" was held at Mulhouse inside the Musée among all these Bugatti.