The 72-year-old, who stays in touch with his fans through other digital platforms too, had recently crossed 18 million followers on social networking site Facebook.
"12 MILLION!! IT IS NOW OFFICIAL!!! Thank you all that follow... may you continue ... and may I be with you each day ... my love!," Big B tweeted Sunday.
Meanwhile, he is using digital platforms to promote cleanliness campaign.
On Twitter he wrote: "Bharat swachh zaroor banega! Send your thoughts/ questions/ suggestions with #swachhindia to me. Cleanathon Live now!," he tweeted.
He also took to his blogging site srbachchan.tumblr.com to talk about his participation in SwachBharat campaign.
"SwachBharat campaign ... to derive funds and raise donations through a charity appeal for the entire day 9 am - 10 pm, a telethon on NDTV," he blogged Sunday.
