You need to store the number somewhere and access it somehow. There are many ways to do this. I have personally solved problems of this nature with saving the number in a file on a file server, using DBI, and using Cache::Memcached. All are appropriate solutions in the right situation.

The trade-offs are that the file server is the easiest to implement, the database is the most flexible (particularly as you start to have more complicated data structures), and the third is probably going to run fastest.

I would personally lean towards either the file server or the database.