You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
5-hydroxy-2,2,6,6-tetramethyl-4-[2-methyl-5-(1-oxidopyridin-1-ium-2-yl)phenyl]pyran-3-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H23NO4
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