How many F40 are left?

I'm curious, could you tell me how many Ferrari F40 sports cars are still in existence today? It's a legendary model that's garnered a lot of attention among car enthusiasts and collectors alike, so I'm quite fascinated to know the exact number of F40s that have survived the test of time. Is there a reliable source that keeps track of this information, or would it be difficult to ascertain the exact number due to the rarity and exclusivity of this iconic vehicle?