XRP is the native currency of the Ripple network that only exists within the Ripple system. XRP are currently divisible to 6 decimal places, and the smallest unit is called a drop with 1 million drops equaling 1 XRP. There were 100 billion XRP created at Ripple's inception, with no more allowed to be created according to the protocol's rules. As such, the system was designed so XRP is a scarce asset with decreasing available supply. Not dependent on any third party for redemption, XRP is the only currency in the Ripple network that does not entail counterparty risk, and it is the only native digital asset. The other currencies in the Ripple network are debt instruments (i.e. liabilities) and exist in the form of balances. Users of the Ripple network are not required to use XRP as a store of value or a medium of exchange. Each Ripple account is required, however, to have a small reserve of 20 XRP (US$6.58 as of May 16, 2017). The purpose of this requirement is discussed in the anti-spam section.