I know it doesn't take much to code something like this myself, but if Qt already has the functionality, it makes sense to use that rather than bloating my source code.

64-bit integer such as: 17753210880. I want it displayed as: 17,753,210,880. Does Qt support this already or do I have to write my own method? In which case I'm not sure whether the best way is mathematically or using QString to insert the commas...