Quote:
Originally Posted by Stargate38
If interpreted as either Base25 or Base30, it's prime:
M2133277 (Base25) = 134776610807 (Base10)
M2133277 (Base30) = 482624813017 (Base10)

Hmm. I get something quite different.
2133277 (Base 25) = 499,267,057 (base ten), which is prime per
https://www.alpertron.com.ar/ECM.HTM;
2133277 (Base 30) = 1,484,813,017 (base ten) which is divisible by 61, so the corresponding Mersenne number is
composite also, divisible by M61.
(base conversions performed with
https://calculator.name/baseconversion.php; confirmed with
https://www.rapidtables.com/convert/...converter.html)
The corresponding Mersenne numbers would have ~150,000,000 and ~447,000,000 decimal digits, respectively, not 12.
M
499267057 has no factor below 2
^{73} greater than 1.