There are four fixed points (mod 1) of Minkowski's question mark function, namely , 1/2, and , where is a constant known as the Minkowski-Bower constant
(Bower 1999, Finch 2003, pp. 441-443). The value of is given by
Bower, C. "Fixed Points of Minkowski's Function." Unpublished note, 1999.Finch,
S. R. "Minkowski-Bower Constant." §6.9 in Mathematical
Constants. Cambridge, England: Cambridge University Press, pp. 441-443,
2003.Sloane, N. J. A. Sequence A048819
in "The On-Line Encyclopedia of Integer Sequences."