You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 2-N-[(2-chlorophenyl)methyl]-4-N-[2-(3,4-dimethoxyphenyl)ethyl]pyrimidine-2,4-diamine by IUPAC nomenclature, provide its molecular formula.
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C21H23ClN4O2
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