It is more likely theme is adding numbers rather than WordPress.
Find out the css style associated with the numbering and set its display value to none. If you are using a browser based on Google Chrome you can highlight the article numbers, right click and select Inspect.
Then, under the Appearance | Customize menu item in your admin dashboard click “Additional CSS”. Add the css style you wont to override, for example; if your style is article_id_number do the following.
.article_id_number {display:none;}
Save the changes and reload your page. The number should be gone. This trick works for anything you don’t want displayed, similarly you can override your theme css for any other elements.
Note: If the id number and the article title share the same css style the above wont work for you. In which case contact your theme developer and they might include an option to remove the numbers.
Edit: See my comment below regarding down vote!