I would mention the blog, for sure, especially if it is relating to the Topic of studies. It lifts the CV more than pushes it down, as it shows that you are genuinely interested in the field as well as devoted to started projects (it is not easy to keep a blog!). Moreover, you could mention it as an experience in communication with the masses and depending on an Institution you are applying to, it might be a huge benefit, as professionals who can communicate their topic to the public are very much wanted.
To mention the number of followers is up to you but I believe if the person reading your profile will be interested in the blog he/she would ask you to tell more about it during the interview, if they do not ask/mention it, most likely it is not important for them. So keeping the numbers to yourself might be an advantage as it would not irritate not interested ones.
At the end all that matters is how you manage to show it as an advantage that would help you in the position you are applying for.