Actually it's 44720, sorry, didn't notice the rounding.
There are only 44720 different balances possible at the same time, for one billion coins, starting from 1, for integer balances. It's the sum of an arithmetic sequence summing to one billion.
For smallest increase 0.01, it's 447114 different balances possible at the same time, still with 1 NXT minimum balance.
Im not following, what is the signifigance of the number 44720 in regards to 1 billion? I feel dumb for not knowing, it seems like I probably should not have to ask this question

1 + 2 + 3 + ... + n = one billion.
The largest so that the sum is not larger than one billion is is 44720. Therefore, there are at most 44720 different balances possible at the same time. Or 447114 for 0.01 step.