The Cortex-M4 includes a single-cycle multiply and hardware FPU, so floating-point math in control loops or audio processing doesn't bog the core.
The 0.4 mm or 0.5 mm ball pitch typical of WLCSP means the escape routing uses microvias or fine-line traces. The 36 I/O count leaves room for a sensor array plus a display or UART bridge.
Peripherals include I²C, SPI, UART/USART, USB OTG, SDIO, I²S, and IrDA, plus a 10-channel 12-bit ADC. The internal oscillator trims the BOM by one external crystal for many applications.