The course "Complex Variables with Applications" typically requires Differential Equations as a prerequisite, particularly in programs like the one offered by MIT. This course encompasses both pure mathematics, often referred to as Complex Analysis, and applied mathematics, indicated by its focus on real-world applications. While there is no standardized requirement across all institutions, some colleges may only require a calculus sequence and an introductory proofs class as prerequisites. For those seeking a good textbook for this course, recommendations may vary, but it's essential to choose one that balances theoretical and practical aspects of complex variables.