A recent survey of 8 social networking sites has a mean of 13.1 million visitors for a specific month. The SD was 4.1 million find the 95% confidence interval of the true mean.

Now I know what formula to do but I can't match the answer, it should be 9.7 < mean < 16.5 here's what I did please let me know what I'm doing wrong:

13,100,000 - 2.365 * (4,100,000 / 8^5
13,100,000 + 2.365 * (4,100,000 / 8^ 5

The answer doesn't come out anywhere near what it should be, thanks for your time, I really appreciate it.