You got it a little mix up and wrong
Page number = logical address / page size in this case is 21205 / 1024 = 20
Offset = logical address mod page size in this case is 21205 mod 1024 = 725

Sources:
http://www.yorku.ca/pkashiya/cse1520/Paged%20memory%20technique.htm http://www2.cs.uregina.ca/~hamilton/courses/330/notes/memory/paging.html

You got it a little mix up and wrong
Page number = logical address / page size in this case is $\frac{21205}{1024} = 20$

Offset = logical address mod page size in this case is $21205 \mod 1024 = 725$

Sources:
http://www.yorku.ca/pkashiya/cse1520/Paged%20memory%20technique.htm http://www2.cs.uregina.ca/~hamilton/courses/330/notes/memory/paging.html