The Satoshi Nakamoto (SN) is often cited as having put some surprisingly deep thinking into this problem and made some impressively hard choices and educated guesses in order to provide a currency with a fixed minimum(*) and maximum size yet still able to cover all use cases that the currency might face well into the future even if widely adopted by most people on the planet (for a light introduction see under heading “The 21 Million BTC limit”, or more details on the original bitcoin crypto mailing list). Everything from where and why SN chose the decimal place to be where it is to the “lowest money of account” bit size 2^50.899 ~2.1 quadrillion Satoshis choice is no accident and really very clever in more ways than one. On divisibility however, enough room to allow pricing low value 1 bit of data, and still reasonable to use when valuing expensive mansions years from now. Divisibility is a core fundamental characteristic of all in-use currencies and extremely important since if you cannot value any good or service in the currency, then what good is it. Words you often see cropping up are “usability” and “familiarity” when it comes to this topic as well (I mentioned more on the importance of that here).
Then “Safecoin” would be as the Satoshi is to Bitcoin, as near to or as being the lowest unit of account - and people would use it just as often to value goods and services i.e. not much so probably a poor choice of what to call a Safecoin. Agreed that 4 billion total of the lowest unit of account is simply not enough to be useful in the long term and far from Bitcoins ~2.1 quadrillion.
(*) Satoshi is the first pass smallest unit of account, and other smaller divisions could be added by consensus in the future… if a consensus to do so could be reached that is. Also Bitcoin is often criticised for being unwieldy with the decimal point when pricing some goods and services but this is short term thinking IMHO, what value will things have in 50 years and where will the decimal place go then? How can anyone launch a fixed total count supply currency and realistically be able to predict what value the market will price 1 standard unit of it (a “Bitcoin”, “Safecoin”…) at a few years from now? In the end it is all an interface and naming convention problem anyway - the trick is to keep it consistent and familiar so that it remains usable to normal everyday non technical people.