If I convert it I get 26 digits
No, you're right. Not every combination of the words results in a 27 digit number. PhemexBTCETHXRP gives 27 characters, while BTCETHXRPPhemex only gives 26. I didn't actually bother to check which combinations were 26 and which were 27, it would have taken longer to do that than it took to just automatically check them all as I did.
i did the same with 2 alternative additional words: Satoshi and Dorian (it is his picture after all!). used alternative lower case and upper case and both base58 and UTF8 encoding to decode to bytes then to a biginteger in both little and big endian and combined it with the prime as concatenation of the numbers and also with bytes again in both little and big endian. nothing worked

Pkscript OP_RETURN
68747470733a2f2f6b6579732e6c6f6c2f626974636f696e2f7b70677d
I have no idea what to make of that.
hex -> byte -> UTF8 and you'll see (it is advertising keys.lol site)