Approximately how many people have completed a full marathon and half marathon?
That's a hard one you'd need the finishing numbers of every marathon and half marathon in every country in every year since they began. You'd also need all the data from every runner who's ever done either inb training. A crazy question.
That said if you somehow managed to miraculously collate that data you couldn't include Katie Price in the total number. Despite promising half the world she ‘would crawl to/over the finish line' if she had to, she threw in the towel after 7 miles of the 2018 London marathon.
Apparently she was suffering from black eyes and concussion.