The df command with the -i or --inodes flag can be used to list the number of inodes being used by a filesystem.

df --inodes

Something like this should be returned.

Filesystem                 Inodes   IUsed   IFree  IUse%   Mounted on
/dev/mapper/rootvg-lv_opt  2097152  1807492 289660   87%   /opt

The -h or --human-readable flag can be used to display the size in bytes, kilobytes, megabytes or kilobytes.

df -hi

Something like this should be returned.

Filesystem                 Inodes   IUsed   IFree  IUse%   Mounted on
/dev/mapper/rootvg-lv_opt  2.0M     1.8M    283K   87%   /opt