The figure represents a drop of around 160k on last week's opener but a rise of around 330k on the second episode from last year's series.
Spinoff show The Xtra Factor brought in 1.29m (6.9%) for ITV2 in the hour from 8.15pm, with a further 169k (0.9%) tuning in on timeshift. Repeats of both shows snagged 525k (5.9%) and 239k (5.9%) on ITV2 from 11.15pm.
After The X Factor on ITV1, gameshow The Cube managed 4.84m (23.9%) in its second week, an impressive retention of 88% from last week's premiere. A screening of Miami Vice followed with 1.67m (9.8%).
On BBC One, Total Wipeout: Champion Of Champions delivered 3.36m (18.1%) at 6.30pm, then National Lottery: Guesstimation appealed to 2.74m (13.1%). The draw itself was seen by 4.2m (21.1%) and a subsequent screening of comedy movie Meet The Fockers amused 3.99m (20.1%).
Coverage of The Proms took 815k (4%) for BBC Two from 7pm, then two hours later, a rerun of Have I Got A Bit More News For You interested 2.27m (11.2%).
A double-bill of ER managed 491k (2.4%) and 642k (3.2%) for Channel 4, then the latest Big Brother update ensnared 1.36m (6.9%).
Five's NCIS double-bill picked up audiences of 1.1m (5.3%) and 1.7m (8.4%) from 7.20pm. CSI claimed 1.5m (7.6%) and Law & Order put in 1.03m (6.4%).
Overall, ITV1 led primetime with a share of 25.3% to BBC One's 19.6%. Five was third with 6.7%, followed by BBC Two with 6.2% and Channel 4 with 4.7% (+1: 0.4%).
BARB ratings data supplied by Attentional