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.

Fiii Coin is developing an ecosystem designed to promote the wide spread adoption of a variety of cryptocurrencies. Their payment terminal will be compatible with wide range of cryptocurrencies, and will be comprised of a wallet, exchange, and DApp development plugins. The Fiii blockchain has a Delegated Proof of Capacity (DPoC) consensus mechanism.

Alibaba Coin is a digital currency that plans to implement blockchain-based facial recognition technology that will allow users to make transactions by showing their faces to a merchant's camera. Alibaba Coin was created by a company in Dubai, and has no relation to the Chinese online retail giant.