From TDN

In mathematics, a power of two is any of the nonnegative integer powers of the number two; in other words, two times itself a certain number of times. Note that one is a power (the zeroth power) of two. Written in binary, a power of two always has the form 10000...0, just like a power of ten in the decimal system.

2^1       =    2
                 (1 digits)
2^2       =    4
                 (1 digits)
2^3       =    8
                 (1 digits)
2^4       =   16
                 (2 digits)
2^5       =   32
                 (2 digits)
2^6       =   64
                 (2 digits)
2^7       =  128
                 (3 digits)
2^8       =  256
                 (3 digits)
2^9       =  512
                 (3 digits)
2^10      =    1,024
                 (4 digits)
2^11      =    2,048
                 (4 digits)
2^12      =    4,096
                 (4 digits)
2^13      =    8,192
                 (4 digits)
2^14      =   16,384
                 (5 digits)
2^15      =   32,768
                 (5 digits)
2^16      =   65,536
                 (5 digits)
2^17      =  131,072
                 (6 digits)
2^18      =  262,144
                 (6 digits)
2^19      =  524,288
                 (6 digits)
2^20      =    1,048,576
                 (7 digits)
2^21      =    2,097,152
                 (7 digits)
2^22      =    4,194,304
                 (7 digits)
2^23      =    8,388,608
                 (7 digits)
2^24      =   16,777,216
                 (8 digits)
2^25      =   33,554,432
                 (8 digits)
2^26      =   67,108,864
                 (8 digits)
2^27      =  134,217,728
                 (9 digits)
2^28      =  268,435,456
                 (9 digits)
2^29      =  536,870,912
                 (9 digits)
2^30      =    1,073,741,824
                 (10 digits)
2^31      =    2,147,483,648
                 (10 digits)
2^32      =    4,294,967,296
                 (10 digits)
2^33      =    8,589,934,592
                 (10 digits)
2^34      =   17,179,869,184
                 (11 digits)
2^35      =   34,359,738,368
                 (11 digits)
2^36      =   68,719,476,736
                 (11 digits)
2^37      =  137,438,953,472
                 (12 digits)
2^38      =  274,877,906,944
                 (12 digits)
2^39      =  549,755,813,888
                 (12 digits)
2^40      =    1,099,511,627,776
                 (13 digits)