The Patriots began their season at home with an AFC duel against the Cincinnati Bengals. After a Bengals punt, the Patriots scored the first points of the game, racing 72 yards in 5 plays, scoring on a 9-yard touchdown pass from Tom Brady to Wes Welker. Following a Bengals punt, the Patriots marched all the way to the Bengals 14, but had to settle for a 32-yard field goal by Stephen Gostkowski, extending the lead to 10-0. On the third play of the Bengals next drive, Cedric Benson  fumbled with Rob Ninkovich recovering at the Bengals 34. The Patriots only gained 4 yards and Gostkowski missed a 47-yard field goal, keeping the score 10-0. After another Bengals punt, the Patriots engineered a 10 play, 80-yard drive, scoring on another touchdown pass from Brady to Welker, widening the lead to 17-0. The Bengals reached Patriots territory for the first time on their next drive, but Gary Guyton intercepted Carson Palmer at the 41 and returned it 59 yards for a touchdown, giving the Patriots a big 24-0 lead. The Bengals finally struck on their next drive, driving to the Patriots 35, and Mike Nugent hitting a 53-yard field goal, making the score 24-3. After Ben Tate returned the ensuing kick 38 yards to the Patriots 32, the Patriots reached the Bengals 37, but Gostkowski missed the 55-yard field goal attempt wide right. Palmer connected with Jordan Shipley for a 51-yard gain on the last play of the first half, but they couldn't reach the end zone and the Patriots led 24-3 at halftime. Tate returned the opening kickoff of the second half 97 yards for a touchdown, blowing the game open 31-3. The Bengals countered with a 12 play, 85-yard drive, in just under seven minutes, scoring on a 1-yard touchdown pass from Palmer to Jermaine Gresham, trimming the deficit to 31-10. After a Patriots three-and-out, the Bengals continued their comeback, marching 74 yards in 12 plays, scoring on a 28-yard touchdown pass from Palmer to Chad Ochocinco, trimming the deficit to a manageable 31-17. The Patriots ended any hope of a Bengals comeback on their next drive, engineering a 14 play, 81-yard drive, in nearly eight minutes, scoring on a 1-yard touchdown pass from Brady to rookie Rob Gronkowski, increasing the lead to 38-17 midway through the fourth quarter. The Bengals answered, racing 76 yards in under four minutes, scoring on a 1-yard touchdown run by Benson, bringing the score to 38-24 with just under four minutes to play and giving the Bengals some hope, but the Patriots got the ball after Malik Johnson was flagged for illegal touch on the onside kick. The Patriots drove all the way to the Bengals 7 and turned the ball over on downs, draining over two minutes off the clock. The Bengals ran out the rest of the clock and the Patriots won the game.
Question: How many points were the Patriots winning by at halftime?
Answer: 21