"The seventeen turtles are slow."
Translation:De zeventien schildpadden zijn langzaam.
It is quite common in everday speech. Depending on how much you are articulating and how casual the conversation is.
How much a person erodes the n varies per person. Some never say it some you always hear atleast a hint of the n.
Never pronouncing it at all, like a clear cut can sound a bit uneducated especially if you emphasise the last vowel. (Loopûh or loopa).
So safest bet is still pronounce the n but nearly inaudibe. So your mouth still makes the shape for the n but you don't really hear it. (That way there is less chance to turn the last vowel into a sound that sounds less educated)
Hope this helps.