Assuming the split is computer-generated based on a parameter, why not use the last three digits and cut it into 4096 pieces, where each chunk is under 64KB? If your bandwidth bill is small it won't matter (ie: not worth the time involved) but if you get a bunch of traffic your cost is 1/16th of what it would have been. Also, to the user the site will be way more responsive as the download will happen quicker.