Probability of many coin flips coming up heads 65% etc.

#1
Hello, I am wondering how to calculate what the probability would be of flipping a coin, say, 250 times and having it come up heads 65% of the time. Or 500 times and 90%. Maybe I should be asking how to calculate if it will be at LEAST 65%, at least 90%, etc. I am very interested in this problem.

Thanks a lot.