All angels, that are in heaven, are saints (or holy).
catholic.com/thisrock/quickquestions/keyword/St.%20Raphael
<<Q:“ Please tell me how an angel becomes a saint, as in St. Michael the Archangel.
”A: The good angels are saints because God created them in a state of holiness or sanctity. He also enabled them to make a free choice for or against him. Those that made the choice for him were confirmed in their holiness. Those that chose against him lost their holiness.
Of those angels who remained in holiness, Scripture tells us the names of three—Michael (Dn 10:13), Gabriel (Dn 8:16), and Raphael (Tb 12:15). It became customary for Christians to speak of them as holy—“Holy Michael,” for example, which in Latin is Sanctus Michaelus. This then gets translated into English as Saint Michael.
There was no official canonization of these angels. Like the human saints in the first part of Church history, they were recognized as saints by popular acclaim rather than by papal decree.
God has chosen to keep the great majority of the angels anonymous to us in this life, and so we simply pray to “the holy angels” or one’s guardian angel without knowing their names.>>
btw, we are all “saints” because we are made holy (or set apart) by our baptism. The Church officially names Saints so that we have people to look up to–to be role models for how to live saintly lives here on earth and to be with God in heaven.