Most cameras doesn’t even have an ISO 25600 setting. It is only needed in very low light handheld photography.
For most Aps-C cameras it is the highest available setting. In Full frame cameras ISO 25600 can even be okay, as these cameras has better high iso performance.
Only in very low light needed this high setting. In order to have more usable images some additional noise reduction can be very useful (like Noise ninja or Gaussian blur in some cases e.g sky)