33 characters in the Combining Diacritical Marks for Symbols Unicode block.
U+20D0COMBINING LEFT HARPOON ABOVEU+20D1COMBINING RIGHT HARPOON ABOVEU+20D2COMBINING LONG VERTICAL LINE OVERLAYU+20D3COMBINING SHORT VERTICAL LINE OVERLAYU+20D4COMBINING ANTICLOCKWISE ARROW ABOVEU+20D5COMBINING CLOCKWISE ARROW ABOVEU+20D6COMBINING LEFT ARROW ABOVEU+20D7COMBINING RIGHT ARROW ABOVEU+20D8COMBINING RING OVERLAYU+20D9COMBINING CLOCKWISE RING OVERLAYU+20DACOMBINING ANTICLOCKWISE RING OVERLAYU+20DBCOMBINING THREE DOTS ABOVEU+20DCCOMBINING FOUR DOTS ABOVEU+20DDCOMBINING ENCLOSING CIRCLEU+20DECOMBINING ENCLOSING SQUAREU+20DFCOMBINING ENCLOSING DIAMONDU+20E0COMBINING ENCLOSING CIRCLE BACKSLASHU+20E1COMBINING LEFT RIGHT ARROW ABOVEU+20E2COMBINING ENCLOSING SCREENU+20E3COMBINING ENCLOSING KEYCAPU+20E4COMBINING ENCLOSING UPWARD POINTING TRIANGLEU+20E5COMBINING REVERSE SOLIDUS OVERLAYU+20E6COMBINING DOUBLE VERTICAL STROKE OVERLAYU+20E7COMBINING ANNUITY SYMBOLU+20E8COMBINING TRIPLE UNDERDOTU+20E9COMBINING WIDE BRIDGE ABOVEU+20EACOMBINING LEFTWARDS ARROW OVERLAYU+20EBCOMBINING LONG DOUBLE SOLIDUS OVERLAYU+20ECCOMBINING RIGHTWARDS HARPOON WITH BARB DOWNWARDSU+20EDCOMBINING LEFTWARDS HARPOON WITH BARB DOWNWARDSU+20EECOMBINING LEFT ARROW BELOWU+20EFCOMBINING RIGHT ARROW BELOWU+20F0COMBINING ASTERISK ABOVE