Hey Vikas!

Please provide the name of the college or the entrance exam(if any) for which you have forgotten your registration number. If you are talking about the college registeration number, then you can find your registration number in your ID card or even the admit card. You may check out your forms which you must have filled initially. Then also, if you are not able to find then seek help from your college. There must be your Teacher-in-charge or proctor or mentor who you can contact.

And if you are referring to some entrance exam registeration number, then you may mention the name of the exam in the comment section. Otherwise you may try to find your registration number by checking your mail Inbox, you must have received a mail when you would have registered or you can login from your account and in case you forgot the password, click on the forgot password option and then you can set up the new password and get your details.