The obvious way to read a number aloud is to read it as though it had been spelled out in words rather than given as digits. So 245 is read aloud as doscientos cuarenta y cinco.
What about numbers which are just identifiers like Boeing 737, hotel rooms, numbers in catalogues like Bach's cantata Wachet auf BWV 140. Is it optional whether to read them as a number or to spell out the digits? So would I say Boeing siete tres siete