"Here we experimentally demonstrate the factorization of two bi-primes, 4088459 and 966887 using IBM's 5- and 16-qubit quantum processors, hence making those the largest numbers that have been factorized on a quantum device."[1]

It looks like some real progress has been made with qbit quality and stability in the last few years! I think that 21 figure held for quite a while. Maybe it still does hold and I'm misunderstanding some of the nuance.

1 - https://arxiv.org/abs/1805.10478