from 2018 regarding the BBC drama Wanderlust uses this exact number in its URL. It is possible a video clip from this episode was saved with the article's ID as the filename.
: A user manually added ".mp4" to a file that already had a hidden extension. 6181147.mp4.mp4
: In specialty toy catalogs, 6181147 is the product code for a Safari Contour Puzzle Go to product viewer dialog for this item. from 2018 regarding the BBC drama Wanderlust uses