The immortal numbers were defined and researched by Daniel Marschall and are defined as integers, which contain themselves as suffix when raised to a power.

- 1. Definitions
- 2. Branch graph notation
- 3. Immortal number search
- 4. Graphical plots
- 5. Miscellaneous proofs, theorems and attributes
- 6. Open questions and unproven theorems

*Definition*: A number is "immortal" (with power 2 at base 10), if it satisfies following equation:

*Example*: The number 625 is immortal at base 10, because 625 x 625 = 390625

*Definition*: A number is "immortal" with power at base , if it satisfies following equation:

*Example*: The number 2047 ( 3777_{(8)} ) is immortal with power 3 at base 8, because
3777_{(8)}^{3} = 77720013777_{(8)}

The set contains all immortal numbers with power at base .

*Definition*:

*Example*:

The "immortality" of a tuple is defined by the amount of immortal numbers divided by the maximum length of these numbers. The higher the maximum length is chosen, the more accurate is the immortality. The unit of measurement can be optionally written as ("Immortals per Digit"). Since the numbers are always immortal, they will be exluded from this calculation.

*Formal definition*:

*Example*: For base 10, power 3, there are 1176 immortal numbers with length of 1..100 digits, exluding 0 and 1. The immortality of is therefore approximately

Here you can find a plot that compares the immortality of various tuples.

There are base/power-tuples where only the numbers are immortal. These base/power-tuples are called "pseudo-immortal". An example is .

Their immortality is zero because:

Here you can find a plot that shows the values of some pseudo-immortals.

Super immortal numbers are numbers which are immortal to every tuple. Only the numbers satisfy this property (see proof).

Immortal numbers can be written in graph with "branches".

In **base 10, power 2**, things are quite easy: There are only 4 branches 0, 1, 5 and 6. The branches 0 and 1 are trivial branches and have no children.

In branch 5, the immortal numbers are 5, 25, 625, 90625, 890625, 2890625, 12890625, 212890625, 8212890625, ...

In branch 6, the immortal numbers are 6, 76, 376, 9376, 109376, 7109376, 87109376, 787109376, 1787109376, ...

In this case, immortal numbers of base 10 power 2 can be generated using a tree node and adding a single digit in front of it. Additionally, the sum of the pairs of digits below branch 5 and 6 always add up to 9.

However, there are more complex graphs, for example **base 10, power 3**:

*Credits*: The graphs were created with mind-map-online.de

There has been a huge effort to find immortal numbers with several million digits. A special algorithm, optimized extensively using SSE/MMX technology, has been written to archive this task.

On July, 9th 2019, the immortal number of base 10, power 2 with **1.1 billion digits** was found. (Note: The double-verification started 2017 is still running)

Download the giant immortal numbers:

- 1.1 billion digits long number of branch 5 (zipped, 493 MB)
- 1.1 billion digits long number of branch 6 (zipped, 493 MB)
- 1.1 billion digits raw data (reversed order), can be used to continue the calculation using the tool below (508 MB)
- Statistics file created by the generation tool (3 MB)

Get the tool to calculate these numbers (Source codes written in C)

*Credits*: The search for giant immortal numbers at base-10-power-2 were only made possible by the users of the
matheboard.de thread who contributed the algorithm for finding base-10-power-2 numbers
as well as the contributor of this StackOverflow question
who has showed me how to speed up the algorithm using SSE/MMX instructions.

A rather trivial search algorithm has been developed to find all immortal numbers between base 2 and 36 and **power 2 till 10**, with a maximum length of **100 digits**.

Get a list of immortal numbers with max length 100 digits, for powers 2 till 10, with following base:

02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36

Base 10 filtered:

A red x denotes an immortality of zero. Dots denote an immortality.
The bigger the dots are, the greater is the immortality of .

Green dots denote an immortality of .

Blue dots denote an immortality of .

We want to prove that

Let's begin with:

With mathematical induction we can now prove that

therefore

Since all immortal numbers of power are also immortal in power , we have now proven that

*Theorem*: For every number there is a tuple so that .
In other words, *every* number is immortal to some specific base and power.

*Note:* The theorem of complete immortality also leads to the conclusion:

*Proof:*

(0) Let with an arbitary value.

(1) Let be a prime that is not a prime factor of ( ), then is not a prime factor of either ( ).

In other words: .

(2) Since we have , we can create following term using the Fermat-Euler theorem:

Transforming it a bit, we get:

(3) If we now define and insert the definition of from above, then we get:

which is equivalent to:

*Credits*: Many thanks to Finn from matheboard.de
for showing me how to prove this theorem!

We want to prove that the only super-immortals are 0 and 1.

(1) First, we verify that 0 and 1 are immortal to every :

(1.1)

(1.2)

(2) To prove that the only super-immortals are 0 and 1, we want to find a tuple for every that will cause :

(3) The definition of an immortal number is

We can see that a number can only be immortal if is a number that has more digits (in the notation of base ) than .

(4) If we choose a high enough base , then and would have the same amounts of digits, and therefore could not be immortal.

So, we need to find a , so that .

If we choose , we get:

If , then and therefore:

, which is true, if .

(5) We continue by taking the general definition of an immortal number

which can also be written as:

Since and ( because if ) :

, which is false if .

*Side note:*

If , then:

(6) Therefore:

(7) Bringing together the results of step (1) and (6), we can conclude:

Help and suggestions are welcome!

#1:

#2:

#3: Is there a base that does not have any non-trivial (not 0,1) immortal numbers?

#4: Is there a power that does not have any non-trivial (not 0,1) immortal numbers?

#5: The topic "Base B / Power P" is not researched very much. It is not known how to find "Base B / Power P" immortal numbers without brute-forcing them.

Various notes and other stuff: runs, old_notes

*Credits*: The equations were generated with the Codecogs Online LaTeX Editor.

*Last update: 13 July 2019*

Contact: info&daniel-marschall.de