Primecoin is a cryptocurrency based on finding prime numbers. Identifying prime numbers plays a central role in cryptography. Primecoin's unique Proof-of-Work (PoW) consensus mechanism is able to increase transaction speeds and improve energy efficiency.
The network searches for special prime number chains known as Cunningham chains and bi-twin chains, which are of interest in mathematical research.

Lightning Bitcoin is a cryptocurrency protocol with a DPoS consensus mechanism. It is a hard fork of Bitcoin that was created with the goal of improving transaction speeds and scalabilty. Lightning Bitcoin's on-chain governance system enables LBTC holders to vote for the blockchain improvement proposals and the delegates who maintain the network as Lightning Nodes. Lightning Bitcoin is not related to the Lighting Network, which is an off-chain protocol built on the Bitcoin blockchain.

PIRL is a community based blockchain project focused on making cryptocurrencies more accessible. It was the first blockchain to introduce an Ethash-based masternode. Their goal is to develop a comprehensive DApps hosting infrastructure that will be easy to use. Their Poseidon platform is designed to be an on ramp for users without any technical knowledge. PIRL's multi-tiered masternode network has an ASIC-resistant Proof-of-Work (PoW) consensus mechanism, and is powered by the PIRL coin. The company plans on developing features, such as: decentralized file storage, messaging, and escrow services for payments.