7 is the only real number D for which the equation 2n − D = x2 has more than two answers for n and x all-natural. Particularly, the equation 2n − 7 = x2 is known as the Ramanujan–Nagell equation. Jahannam has seven gates which are open continually. (Qur’an – https://jessicai271sgr2.digitollblog.com/profile