Hello Dear,

According to you, you got 81.6 percentile in JEE Mains 2021 then your rank would be around 188232 - 211600 . You do not mention your category and state region. So I am assuming that you belong to general category.  There is chance to get admission in colleges in U.P  that are accepting JEE Mains scores such as

Raj Kumar Goel Institute Of Technology,

Mangalmay Group Of Institutions,

ABES Engineering College,etc.

You can predict rank from the link given below :-

To more information about  JEE Mains 2021:-

JEE Main 2021 Exam Phase 4 Starts - Analaysis, Answer Key, Result , Scorecard, Question Papers (careers360.com)

Hope this information helps you...

Best of luck :)