Since you have received 21000 rank in the JEE, then there is a probability that you would be able to get the CSE branch.
I would recommend to make a list of college's you want to apply to and email them your score.
You can check your rank using our rank Predictor.
There are still plenty of good colleges that you can apply for and pursue the subject of your dreams.
And for the further details, if you have any query you can even visit our website, where there is a detailed description which would be quite helpful for you
