Not to be confused with Apocalypse number.

Apocalyptic numbers are numbers of the form 2n containing the digits 666 in their decimal expansions.[1] 2157 is the smallest apocalyptic number:


2n is an apocalyptic number for n = 157, 192, 218, 220, 222, ... (OEIS A007356). These values of n become increasingly dense, and as \(n \rightarrow \infty\), the probability of \(2^n\) being apocalyptic becomes 1. Thus, when sufficiently large, apocalyptic numbers cease to be interesting and non-apocalyptic powers of two become more of a novelty.

There are 3,716 non-apocalyptic numbers of the form 2n for \(0 \le n \le 1,000,000\), the largest of which is \(2^{29,784}\). From heuristic considerations, \(2^{29,784}\) is very likely the largest one.

Specific numbers

The apocalyptic number 2220 is particularly interesting, being the smallest one containing 666 twice:


It also has the first set of five consecutive sixes.

There are two apocalyptic numbers which are also apocalypse numbers (namely, 22,210 and 22,212).

\(2^{11,666}\) and \(2^{26,667}\) are two non-apocalyptic numbers that contain 666 in their base-2 logarithms. There is an overwhelming probability that there are not any others.

Tetrational apocalyptic numbers

The first apocalyptic number in the form \(^n2\) is \(^52\). Since the last digits of \(^n2\) converge, a 666 will almost surely freeze at some point into the convergent digits. In fact one does so at \(n = 1,213\), and there is a finite (but unknown) number of non-apocalyptic numbers of this form. If \(2^{29,784}\) really is the largest non-apocalyptic power of 2, then \(^42\) is the largest non-apocalyptic power tower of 2.


See also

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