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.

Digix is digital gold on the blockchain. By combining the historical stability of a valuable physical asset with the advantages of a distributed ledger, Digix allows users to benefit from the advantages of both commodities and digital tokens.
Digix has an innovative Proof of Asset (PoA) protocol that allows it it tokenize a physical asset. The PoA protocol tracks an asset through its chain of custody, and enables anyone to verify its existence without an intermediary. Since every DGX = 1 Gram of gold, their platform can be used as a secure and transparent digital marketplace for gold.
Digix is also behind DigixDAO, a platform that allows users to contribute to building a blockchain-based digital gold payment system. They hope to create a decentralized autonomous organization (DAO) that will participate in creating this platform. Instead of issuing shares, the organization will be run by DigixDAO token holders.

Divi is a Proof of Stake cryptocurrency with a masternode system designed to encourage network participation. The project is focused on facilitating adoption of cryptocurrencies by creating a system of incentives for both everyday users and those that help run the networks. Divi's masternode system has five layers of participation and awards users for staking their coins. Divi has an innovative lottery block system that randomly pays out lottery prizes in the form of new coins to network users.