And in any case, because this trick works using only 4 qubits, it can easily be reproduced on any classical computer. So it’s not so useful after all.

via The Mathematical Trick That Helped Smash The Record For The Largest Number Ever Factorised By A… — The Physics arXiv Blog — Medium.

Here’s a paper on this subject:

[1411.6758] Quantum factorization of 56153 with only 4 qubits.