The Blockchain is immutable if:o The number of miners on network is largeo No single miner is larger than the communityo Cost of mining is very high

The Blockchain is considered immutable due to the following reasons:

1. The number of miners on the network is large: This ensures that there is a decentralized distribution of power and control. The more miners there are, the more difficult it becomes for any single entity to take control of the network and manipulate the blockchain.

2. No single miner is larger than the community: This is related to the first point. If no single miner or mining pool controls more than 50% of the network's mining power, it becomes nearly impossible for them to manipulate the blockchain. This is because blockchain operates on a consensus protocol, and if a single miner were to control more than 50% of the network, they could potentially manipulate transactions and blocks, breaking the immutability of the blockchain.

3. Cost of mining is very high: The high cost of mining acts as a deterrent to any entity attempting to control the majority of the network's mining power. The cost of the hardware, electricity, and maintenance required for mining is substantial. This high cost makes it economically unfeasible for any single entity to control a majority of the network's mining power.

Therefore, the combination of these factors contributes to the immutability of the blockchain.