You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-ethyl-2-[4-(4-ethylpiperazin-1-yl)butyl]-3-(1-propan-2-ylpiperidin-4-yl)guanidine;hydroiodide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H45IN6
assistant