SQL> startup
ORACLE instance started.

Total System Global Area 599785472 bytes
Fixed Size 1288820 bytes
Variable Size 192939404 bytes
Database Buffers 402653184 bytes
Redo Buffers 2904064 bytes
Database mounted.
ORA-01172: recovery of thread 1 stuck at block 4545 of file 1
ORA-01151: use media recovery to recover block, restore backup if needed
SQL>

Cause :
  There is block corruption in tablespace.

Solution :

 SQL> shutdown immediate;
 SQL> startup mount;
 SQL> recover database;
 SQL> alter database open;