You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[[3-(4-bromophenyl)-1,2-benzothiazol-6-yl]oxy]-N-methyl-N-prop-2-enylbutan-1-amine is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H23BrN2OS
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