What is 24mm on full frame in aps c?

24mm on full frame gives the view of 16mm on APS-C.

The same view on every common format:

• Medium format (44 x 33): 30mm
• Full frame (yours): 24mm
• APS-C: 16mm
• APS-C (Canon): 15mm
• Micro Four Thirds: 12mm
• 1-inch: 8.9mm
• 1/1.3-inch: 6.7mm
• 1/1.7-inch: 5.2mm
• 1/2.3-inch: 4.3mm

Crop factors are by the sensor diagonal, rounded as they're usually quoted; a format with a different shape (4:3 against 3:2) frames a little differently across the width. More in the focal length converter.

Computed from the sensor sizes, not written by a model.