Looking back over my old tweets on Twitter (as it was once called), I noticed that my first reference to a day count occurred on August 11th 2013. See Figure 1.
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Figure 1 |
It's a fairly unimpressive tweet that, from a mathematical perspective, simply notes that 23506 has four distinct prime factors. I wasn't aware of the Online Encyclopedia of Integer Sequences or OEIS back then, not Numbers Aplenty or most other resources that I now use. The OEIS informs us that 23506 is a member of A029793:
This is because \(23506^2=552532036\) and there are not many numbers in the range up to 40000 that have this property. The numbers that do are:
0, 1, 10, 100, 1000, 4762, 4832, 10000, 10376, 10493, 11205, 12385, 12650, 14829, 22450, 23506, 24605, 26394, 34196, 36215
From Numbers Aplenty we learn that 23506 has properties that make it
- a self number because there is no number that added to its sum of digits gives 23506
- an untouchable number because it is not equal to the sum of proper divisors of any number
- a xenodrome in base 9: 35217 and in base 10: 23506 because all digits are different
- an attractor because its sum of even and odd digits are the same (8)
These are just a few of the special properties that 23506 possesses. I've come a long way since those early days.
