473.91 is the code given to a unique type of Mentor product. Specifically, it is a training solution for product design and development, for both hardware and software. It provides an intuitive and highly customized learning environment with real-time project management and feedback. It has a range of features designed to save time and aid creative collaboration, from product requirements management to sequence diagrams, system architecture, prototyping, and verification. It also offers several advanced features such as hierarchical design trees, resource scheduling, and multi-tabbing editor.