Quote from: rugrats on August 10, 2014, 04:09:54 AM

Quote from: Ayers on August 07, 2014, 02:42:41 PM

was arbitratry for bitcoin also? i remember 21M come up from a math equation or some other calculation

Ethereum's Vitalik Buterin wrote about this last year.

Quote

Thus, all in all, the total number of currency units that will ever exist stands at 2,100,000,000,000,000: 2.1 quadrillion, or about 250.899. In choosing this figure, Satoshi was much luckier, or wiser, than most people realize. First of all, the number is considerably less than 264 1, the largest integer that can be stored in a standard integer on a computer go above that, and the integers wrap around to zero like an odometer.

Second, however, there is another, lower threshold that the total satoshi count manages to fall just below: the largest possible integer that can be exactly represented in floating point format. Integers are not the only kind of number that computers can store; to handle decimal numbers, computers use a format known as floating point representation.

[...]

Notice how scientific notation allows you to express all of these values with reasonable accuracy despite their wildly varying scales. Floating point notation is essentially scientific notation in binary; when you store the number 9.625, your computer stores 1.001101 * 1011 (or rather, it stores 01000000 00100011 01000000 00000000 00000000 00000000 00000000 00000000, which is the same thing in high-precision serialized form). In this high-precision form, the significand (the part thats not the exponent) has 52 bits. What this means is that high-precision (more precisely, double precision) floating point numbers are good enough to exactly store integers up to 253, but not higher if you go higher, you start lopping off digits at the end. Bitcoins 250.9 satoshis are, in exponential terms, just below this maximum.

Very interesting. What about other altcoins (i can think of dogecoin) whose total number is above 21MM. Will they run into problems at some time?