Complex sentence: Number theory (or arithmetic Especially in older sources; see two following notes.) is a branch of pure mathematics devoted primarily to the study of the integers, sometimes called "The Queen of Mathematics" because of its foundational place in the discipline.
Split into simpler sentences: Number theory (or arithmetic Especially in older sources; see two following notes.) is a branch of pure mathematics devoted primarily to the study of the integers. It is sometimes called "The Queen of Mathematics" because of its foundational place in the discipline.