You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[[(2Z,3R,4R,5R)-5-[6-chloro-4-[[(1S)-1-phenylethyl]amino]pyrazolo[3,4-d]pyrimidin-1-yl]-2-ethylidene-3,4,5-trihydroxypentoxy]-hydroxyphosphoryl]methylphosphonic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H28ClN5O9P2
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