Number 6
Alex Galchenyuk is number 27 on the Montreal Canadiens.
Steve shutt Yvan Cournoyer, whose number is among those retired by the Canadiens. (Steve Shutt wore #22) You're correct that Cournoyer's number was retired in his honor (as well as honoring Dickie Moore), but several Canadiens wore #12 after Cournoyer retired in 1979. Keith Acton wore it in the early 80's, as did Serge Boisvert. Mike Keane wore it in the early 90's before he was traded to Colorado with Patrick Roy.
Alexei Emelin is number 74 on the Montreal Canadiens.
Andrei Markov is number 79 on the Montreal Canadiens.
Brandon Prust is number 8 on the Montreal Canadiens.
Brian Gionta is number 21 on the Montreal Canadiens.
Carey Price is number 31 on the Montreal Canadiens.
Christian Thomas is number 60 on the Montreal Canadiens.
Dale Weise is number 22 on the Montreal Canadiens.
David Desharnais is number 51 on the Montreal Canadiens.
Davis Drewiske is number 44 on the Montreal Canadiens.
Douglas Murray is number 6 on the Montreal Canadiens.