The 64-LQFP package (10x10 mm) gives 50 usable I/Os, plus USB OTG, SPI, I²C, and UART interfaces — a common fit for industrial control panels, motor drives, and IoT edge nodes that need floating-point math without jumping to a higher-core-count part.
The 512 KB Flash is organized as 512 K x 8, and the 96 KB SRAM as 96 K x 8. For a typical bootloader + application + config-block split, that leaves room for a second-stage boot and OTA staging area if the application code stays under about 400 KB. The SRAM covers moderate data buffers and stack — if your design needs a large frame buffer or double-buffered display, budget for external SRAM or move to a higher-RAM variant in the STM32F4 family.
ST lists the STM32F401RET6 as Active.