Googology Wiki
Googology Wiki

View full site to see MathJax equation

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:

182,687,704,666,362,864,775,460,604,089,535,377,456,991,567,872

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:

1,684,996,666,696,914,987,166,688,442,938,726,917,102,321,526,408,785,780,068,975,640,576

It also has the first set of five consecutive sixes.

There are two apocalyptic numbers that 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.

Sources[]

See also[]