Apple Makes Developers Update Apps to 64-Bit
With the launch of the iPhone 5s, Apple added support for 64-bit applications. Few developers took advantage of that. However, Apple is making all developers have 64-bit support for all application submissions after February 1. If a developer submits an app that does not support 64-bit, the app will not be added to the App Store.
Many people are updating their apps today, one of them being Amazon. They released an update today with support for 64-bit. Interested developers can learn more about the requirements here.