rt11guru said it. here's another easy way. write down the powers of two in *descending* order, starting with the one that is next smallest after your number. for instance, the power of 2 that comes after 534 is 512 or 2^9. so you write down this list of numbers:
512 | 256 | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
then go through and find the largest of these powers of 2 that is less than your number. in this case, that is 512. put a 1 underneath 512:
512 | 256 | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
1
now subtract that power of 2 from the number you started with. 534-512 = 24. repeat the process. find the largest power of 2 that is less than 24, which is 16. put a 1 under that number:
512 | 256 | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
1 | | | | | 1 | | | |
now subtract that power of 2 from your number. 24-16 = 8. keep doing this until you've reached zero. in this case it only requires one more step, because 8 - 8 = 0. your table at the end should look like this:
512 | 256 | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
1 | | | | | 1 | 1 | | |
now, everywhere that is missing a 1, fill in a 0.
512 | 256 | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
1 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0
that sequence is your binary number. in the case of 534, it is 1000011000.
(sorry, this looks terrible. can't format it properly in this yahoo window. but, each one of those | in the bottom rows should line up with the | in the top row.)