Total number of addresses that start with the same 11 characters = 2^66 / 58^(11 * log2(58))

First, calculate 58^(11 * log2(58)):

58^(11 * log2(58)) ≈ 58^42.614 ≈ 1.2107 × 10^74 (approximately)

Then, divide 2^66 by this result:

2^66 / 1.2107 × 10^74 ≈ 460708775.52

So, the approximate number of addresses that start with the same 11 characters from a key length of 2^66 bits is about 460,708,775.