Primecoin is described as 'Innovative cryptocurrency, a form of digital currency secured by cryptography and issued through a decentralized mining market. Derived from Satoshi Nakamoto’s Bitcoin, Primecoin introduces an unique form of proof-of-work based on prime numbers' and is a cryptocurrency coin in the bitcoin & cryptocurrency category. There are more than 50 alternatives to Primecoin, not only websites but also apps for a variety of platforms, including Linux, Mac, Windows and Android apps. The best Primecoin alternative is Monero, which is both free and Open Source. Other great sites and apps similar to Primecoin are Bitcoin, Ethereum, Litecoin and DASH.