2^ 1=2,2^2=4,2^3=8,2^4= 16,
2 5 = 32, 2 6 = 64, 2 7 = 128 ... you must have found the law of single digits, 2, 4, 8, 6, 2, 4, 8, 6 ... so the single digits of 2 999 are 8.
Let's look for the rule of ten digits again. This is hard to find. Need a little patience, hehe.
2 1 = 2, 2 2 = 4, 2 3 = 8 The decimal number is 0.
2 4 = 1 6 The decimal number is1.
2 5 = 32 decimal number 3
2 6 = 64 The decimal number is 6.
2 7 =128 The decimal number is 2.
2 8 = 256 The decimal number is 5.
2 9 = 5 12 The decimal number is 1.
2 10 = 1024 The decimal number is 2.
2 1 1 = 2048 The decimal number is 4.
2 12 = 4096 The decimal number is 9.
2 13 = 8 192 The decimal number is 9.
2 14 = 16384 The decimal number is 8.
2 15 = 32768 The decimal number is 6.
2 16 = 65536 The decimal number is 3.
……