Out of curiosity I checked, and he's at 6.83M subscribers. According to https://socialblade.com/youtube/c/3blue1brown https://socialblade.com/youtube/c/3blue1br

Out of curiosity I checked, and he's at 6.83M subscribers. According to https://socialblade.com/youtube/c/3blue1brown https://socialblade.com/youtube/c/3blue1brown (not sure how trustworthy the site is, but I believe it should give a general idea) it's 706th channel by subscribers.