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.

ILCoin is a PoW cryptocurrency. Their goal is to become the first cryptocurrency that uses the SHA-256 encryption algorithm to be able to execute smart contracts. The ILCoin is traded on several exchanges under the symbol ILC.

QChi is an Ethereum-based token with no clear benefits. Their marketing materials do not provide any specific information about their roadmap or what advantages it offers compared to other cryptocurrencies.