In their defense, they were probably targeting the Mersenne prime 2^2 - 1 and just made a typo.

ok, it's joke. but for those who don't get it: elliptic curves don't need primes

It’s really impressive no one caught their three previous private key values

They should have gone with 57. Everyone knows it's prime.

https://xkcd.com/221/

it doesn't have to be and it actually never is: this isn't RSA, it's an elliptic curve algorithm. if you'd have read the article, you'd have understood this

The number 4 is very famous.

https://xkcd.com/221/

Hey, that's the same combination I have on my luggage!