I think it's one of the reasons people keep saying bitcoin btc is too expensive, they don't realize you can buy/own fractional bitcoins. My phone has 0.2 btc at the most, and usually less than 0.1 btc
1 satoshi is 100 milionth of a bitcoin 0.00000001 7 leading zeroes.
During the bull market of 2013/14, a new unit was proposed as the default on wallets, but it reverted back. It's called millibit 0.01 which is equivalent to $227 at this moment.
Electrum wallet on the phone does $ conversion (and other fiat currencies) so you can put any fractional bitcoin amount in there for example 0.035974 btc but it's dependent on the exchange configured on the electrum wallet which is selectable.