Primecoin, or XPM, involves a new type of proof-of-work based on searching for prime numbers. Primecoin was created by Sunny King - who also created Peercoin. The block time is one minute and th total number of coins is 3299976 with dynamic difficulty retargetting.
PrimeCoin (XPM) Features
Technology Specifics for PrimeCoin (XPM)
PrimeCoin (XPM) uses the Multiple algorithm and relies on the PoW proof type.