The iPhones have sensors with about a 6 mm diagonal(depending on the model). A typical full frame camera has a diagonal of about 43 mm, so the crop factor is about 7. That means that the lens acts like a lens of 7 times the focal length in terms of field of view. A standard 50mm DSLR lens becomes a 350mm lens in terms of field of view. It is like you take a picture with a full frame DSLR and crop it to 1/7 the size in each direction. You have about as many pixels as the DSLR, but there is blurring due to diffraction because the pixels are so small.

I have a Nikon P900 with a slightly larger sensor, so the crop factor is 6. The lens goes out to an actual 357.5 mm focal length, which is equivalent to 2000mm on a full frame 35mm. I also have a Canon 7D with the 100-400mm zoom, which has an effective focal length of 640mm. I find (YMMV) that I prefer the Canon shots when the right focal length is about 1300mm or less because the larger pixels and less zoom range make a sharper image, even cropped by a factor 2 or so. When the target gets smaller than that, I prefer the Nikon with its higher pixel count. The Nikon will not stop down smaller than f/9.5 because of diffraction, so don't ask it to give you much depth of field.

The arithmetic in this answer is approximate, but accurate enough for the subject at hand.