This book is a selection of 15 papers developed by participants in ICME 13 held in Hamburg , presenting insights from the latest research on the andragogy of adult and lifelong learning of mathematics. It also investigates open questions, such as numeracy and mathematics skills, social and psychological influences on learning environments, as well as economic and political demands. The chapters offer examples, while at the same time highlighting important directions for further research. The book is divided into four parts: The first section provides an overview on the concept of “numeracy”, and the second focuses on adult students who are learning mathematics; the third part presents a teachers’ focus and the final part covers overarching themes. The book is of interest to classroom teachers, university teacher educators, and professional development providers.