AK, turned tptk, but flush also hits. am I missing value on the river?

[scallop]

Villain seems to limp and call alot, but also plays better than one pair hands VERY passively. He previously check/called w AQ on the QQxxx no flush/straight board.

Should I be betting the river here?

Cryptologic
No Limit Holdem Ring game
Blinds: $0.50/$1
6 players
Converter

Pre-flop: (6 players) Hero is UTG+1 with :kd :as
UTG calls, [color=#cc0000]Hero raises to $5</font>, CO calls, Button calls, 2 folds, UTG calls.

Flop: :6c :5c :js ($21.5, 4 players)
UTG checks, Hero checks, CO checks, Button checks.

Turn: :ac ($21.5, 4 players)
UTG checks, [color=#cc0000]Hero bets $17</font>, 2 folds, UTG calls.

River: :2s ($55.5, 2 players)
UTG checks, Hero checks.

Results:
Final pot: $55.5