Bitcoin is on a global decentralized ledger. So long as you keep your private key safe no one can manipulate the entry showing you (through your key) hold X bitcoin. Bitcoin is thus far, far more secure than any centralized financial system like dollars/euro/yen that can be zeroed in an instant by a hacker or a government needing to do some asset confiscation.
No electronic keys are ‘safe’; you know that. Anything and everything can be hacked. The safest place for my cash would be in my Dbl-Door Cannon T65 Safe (7ft wide x 6ft tall x 3ft deep) protected by me.