You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-[[3-[2-(dimethylamino)ethoxy]phenyl]methyl]-3-[1-(4-fluorophenoxy)propan-2-yl]urea by IUPAC nomenclature, provide its molecular formula.
user
C21H28FN3O3
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