You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
8-[2-[[4-(diethylamino)phenyl]methylidene]hydrazinyl]-9-[3,4-dihydroxy-5-(hydroxymethyl)oxolan-2-yl]-1H-purin-6-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H27N7O5
assistant