How did you calculate this? If you take the number of pixels on a standard block, which is 1536 (6 sides with 16x16 = 256 pixels each) and allow every single color combination using RGBA (8 bits for each color plus 8 for transparency for a total of 32 bits; 2^32 = 4294967296) the resulting number is incalculable, at least on any standard calculator; I had to use this site to calculate it (enter 4294967296^1536) and when saved as a text file with spaces removed the size on disk was 14797 bytes (or that many digits).
Even using plain RGB with no transparency, which gives 16777216 colors per pixel, I got a 11098 digit number, and if all 6 sides used the same texture, 1850 digits.
As far as other numbers go, a while ago I made a thread which included calculations for the chances of the largest possible single cave system, which is around one per 8.8 x 10^52 chunks in 1.6.4 and 1.7 x 10^21 in 1.7; both of these are far in excess of the number of unique cave systems that can actually generate, which is about 19 trillion in 1.6.4 and 40 trillion in 1.7 (281 trillion * 1/15 chance per chunk in 1.6.4 and 1/7 in 1.7) so either very likely do not actually exist (in fact, there are 65536 times more worlds than possible unique cave systems and, assuming no overlap, only 20 worlds are required to exhaust every possible "chunk seed", which is also used to determine how most other aspects of world generation appear. This does not mean that you'll find the same things that often since chunks which match will not be in the same patterns). For comparison, every possible Minecraft world has about 2.6 x 10^32 chunks (not accounting for world type, which has no effect on caves or most other non-biome-specific features).