819887 is a user ID, to be precise the one who clicked on the 'Share' link underneath the answer. You can see it in your profile as well:
https://stackoverflow.com/users/819887/surfmuggle. This is to keep track of referrals for the Announcer badge and family.
Now, when you visit that link, you'll see that the final URL does contain both the question and answer ID:
69119268 is the question ID, that's the canonical URL for SEO purposes. The answer ID
69119825 appears twice: once to make sure that you're on the right page if there are lots of answers; the #69119825 is the slug which makes your browser scroll to that answer.
You might be interested in Documentation for Stack Exchange engine URLs? and List of unlinked pages on Stack Exchange sites to learn more.