Seven is the one selection D for which the equation 2n − D = x2 has over two solutions for n and x natural. In particular, the equation 2n − 7 = x2 is named the Ramanujan–Nagell equation. Jahannam has seven gates which might be open up constantly. (Qur’an – https://non-slip-slippers-for-eld78987.blogdeazar.com/38114020/about-7-day-pill-organizers