65536

65536 is a positive integer equal to \(2^{16} = 2^{2^{2^{2}}} = 2 \uparrow\uparrow 4 = 2 \uparrow\uparrow\uparrow 3\). It is the largest power tower of 2's that can be expressed in a compact digital form. \(^52\) has 19729 digits, and \(^62\) has well over a googol digits.

It is found commonly in computer science, being the the number of different values expressible in 16 bits (a short integer).