You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
8-bromo-N-[2-(3,4-dimethoxyphenyl)ethyl]-2-ethyl-6-methylimidazo[1,2-a]pyridine-3-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H24BrN3O3
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