What is a good Hashrate for Bitcoin?

On average, 144 blocks are mined daily and each contains 6.25 Bitcoins.

To attack Bitcoin you need at least 51% of all the hashrate in the world, now that the miners produce 100 quintillion hashes per second that’s becoming a very expensive and unlikely scenario. In short, the more hashing power used to mine Bitcoins, the harder it is for a single person to get 51% of it.

Each Bitcoin block takes 10 minutes to mine. This means that in theory, it will take just 10 minutes to mine 1 BTC (as part of the 6.25 BTC reward).