I am sure your friend don't know much about the bitcoin. Definitely he have heard about some "lottery winners' stories" that someone won the lottery by solving there algorithms etc. Bitcoin is not based on such type algorithms which can easily be hacked or solved, it is not that easy man, infact it is impossible with only a calculator. 
I'm with you on that. Well, mostly, since I still wouldn't completely exclude a possibility of some genius hacking the Bitcoin hashing algorithm, with or without a calculator. As far as I know, it hasn't been proven that there is no easier way to find the hash function used for Bitcoin mining (double SHA-256, if I'm not mistaken).
Hacking bitcoin is not easy work i see, that is almost impossible to do by someone without special skill on hacking or cybercrime. I think the professional hacker must make a hard effort to broken down the security of bitcoin.
The SHA-2 algorithm, which also includes a hashing function known as SHA-256 and used in Bitcoin cryptography, has been developed by the National Security Agency, and they might already have a sort of back-door undermining Bitcoin cryptographic security. That would allow, for example, a successful preimage attack, which in the case of Bitcoin would mean that the NSA might obtain private keys to any Bitcoin wallet (address) in acceptable time frame.
