I had a look at the instructions, video/picture reviews of the set and eBay listings that could potentially show how many bags are missing.
The only solution I could think of would be to place all the bags back in the box, with the instructions and any other parts that were included and weigh the box.
If the weight is noticeably less than what it should be, you may be missing a bag. According to Brickset the Millennium Falcon should weigh 1.83Kg (4.03 lb).
Aside from opening the bags and trying to build the set, you could follow the instructions whilst the bags are sealed and check that you have all the parts as you go along, although this may be quite time consuming.