You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[2-chloro-6-ethoxy-4-[(E)-(1-methyl-2,5-dioxoimidazolidin-4-ylidene)methyl]phenoxy]-N-phenylacetamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H20ClN3O5
assistant