[nielsole]

Not sure what algorithm you use for encryption, but 21 doesn't look like a prime. Maybe run a Miller Rabin test on it? ;)

[sweeneyrod]

It's the modulus of my RSA PK, so the product of two large primes rather than a prime itself. Of course, I can't say what the factors are, otherwise anyone could crack it even if they don't have a quantum computer!