How many pixels a stitched panorama has is not as clear cut I guess. Just because you stitch a panorama at a certain size does not mean that you actually have information for that much resolution - and it's hard to say what size you should stitch at since, for any notrivial panorama, how many source pixels contribute to an area in the output will vary greatly depending on where on the panorama you are looking at due to the nonlinear transforms involved. E.g. stiching an equirectangular projection from ~rectilinear source images will give you much more resolution at the center line compared to the top/bottom, which are just one point stretched across the whole width (for a panorama covering the whole 180 vertical angles).

Then there is also the question of what the source resoltion actually is - most commonly the quoted resolution of a camera (i.e. the "Megapixels" on the maketing material) is usually the number of sensor "pixels" but each of those is only a single color so the resulting image won't really have that many RGB pixels of information even if it is developed at that resolution - the will be quite a bit filled in by interpolation.

Then there is resolution loss from suboptimal focus due to needing to cover a large distance range, lens imperfections or just the air when things are far enough away.

So while the resulting image might have 120 000 000 000 pixels, it might not actually have more than 80 000 000 000 pixels worth of information. That's not to say it isn't impressive, just trying to point out that a simple gigapixel number might not actually say what you might think.

Anywhere to download the original image? Be a cool wallpaper :)