Viacoin is an open source cryptocurrency based on the Bitcoin protocol. Viacoin has a 24 second block time and relatively fast transaction times. It can handle 175 transactions per second without scaling through Segwit or the Lightning Network. The fast transaction times make Viacoin a good option for sending micropayments. The platform also enables users to perform cross-chain atomic swaps between different cryptocurrencies, without a centralized exchange. Viacoin has an Auxiliary Proof-of-Work (AuxPoW) consensus mechanism that allows miners to mine multiple coins, that use the Scrypt algorithms, at the same time. Viacoin's smart contract platform, Rootstock, is compatible with Ethereum smart contracts.

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.

Nano, formerly known as Railblocks, is a cryptocurrency that is focused on enabling fast transactions with no fees. Nano's innovative blockchain architecture utilizes a block lattice structure that does not need miners to confirm transactions.
Nano uses a Delegated Proof-of-Stake consensus.

.