People have been trying to hack bitcoin from years and of course there haven't been any success, The network is extremely strong and is secure enough to stand till now, I am sure it wouldn't be hacked with a calculator or anything like that ever IMO.
Yeah I am confident about the network of bitcoin for it is really strong and it has been proven for a lot of time that is why if some are doubting the network security of bitcoin. We can just be confident and don't mind what they are saying for we know that what is the reality about bitcoin even there are some threats saying that they are going to be able to weaken bitcoins security, well if they think they can then they are crazy.