Added numbers to the image file


I know that WP normally creates thumbnails for all the images and adds something like -80×80, -150×50, etc. But I just noticed that for some strange reason, some of my images in multiple sites are getting added something like: e0921375023 at the end of the file name. Apparently it has something to do with editing the image inside WP.

Does anyone now how to stop this numbers being added?

Thanks for the help!