You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named N,N-diethyl-3-(4-methoxyphenyl)-2-oxo-6-phenyl-4H-1,3,2lambda5-oxazaphosphinin-2-amine by IUPAC nomenclature, provide its molecular formula.
user
C20H25N2O3P
assistant