I only found this:
n sollte hinreichend groß sein; für kryptografische Anwendung
mindestens etwa 200 Dezimalstellen.
which translated means as much as
n should be sufficiently large; for cryptographic application
at least about 200 decimal digits.
This was added in 15th September 2008 before that it has been 100 digits.
So I would assume that it should be at minimum 665 bits. And since the last update is more then 10 years old for sure more today.