I didn't misread it but also initially felt like it was much more. I guess it should be obvious since 2^16 is 65536

A trick for easily estimating powers of two is to remember that 2^10 is about a thousand. Thus 2^20 is about a million, and dividing by four, 2^18 is about 250,000.

Yeah. Just remember that each multiple of 2^10 is approximately 10^3 (1000) and then memorize the single-digit powers of 2: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512. It's useful for doing order of magnitude estimates of multiplications in your head.