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.

PLATINCOIN is a Proof-of-Stake coin that is minted instead of mined. Users participate in managing the network by renting hardware space from the project organizers for a period of 36 months. These computing resources will drive the PoS consensus, and the users that rent the hardware will be rewarded with newly minted PLC coins.

WhiteCoin is a cryptocurrency protocol with a Proof-of-Stake (PoS) consensus mechanism. WhiteCoin's (XWC) marketing materials place an emphasis on security and stability, but do not present details regarding their specific technical advantages or project goals.
WhiteCoin's payment network provides a high degree of anonymity and its PoS consensus model allows XWC coin holders to earn revenue by staking their holdings.