If you want to check how many threads are in the system to compare it with the maximum allowed threads by the system (kernel.threads-max), you can use one of the below two methods.
$ cat /proc/loadavg 0.74 0.93 1.04 3/393 31977
4th column in the above output is related to the current threads number. In this case, there are 393 threads.
You also can check it by run the following command.
$ ps -eLf | wc -l