Quote:
Originally Posted by kriesel
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.

Looks like he took "M" to be a digit with value 22 (as one does), rather than a prefix indicating a Mersenne number.