Range for a fully-loaded 747 is about 5200 nmi, or roughly 25% of the way around the world. That assumes a constant payload weight (not true if the payload is fuel) and a standard fuel load (also not true if the payload is fuel).
You may be correct, and I'm not an airplane performance guy, but I think that, given these factors, a suitably-modified 747 could probably get pretty close to making it.
If you check the numbers you will see that you MIGHT be able to carry 50% more fuel on takeoff. Even with the decreasing weight during flight, that won't get you around the world.