Why does this simple .NET console app have so many threads?

This simple program starts with 15 threads - according to the count. Sometimes during its lifetime it drops a few, but they come back.

class Program
 {
     static void Main(string[] args)
     {
         while (true)
         {
             Console.WriteLine(Process.GetCurrentProcess().Threads.Count);
             Thread.Sleep(500);
         }
     }
 }

I was expecting the process to just have one thread (and my intuition was backed up by this)

Without the debugger, the process has only (!) 4 threads. Surely any CLR stuff would be hidden from my process?

What count is this? Does the process really have that many threads? Why?