Now that bitcoin is more valuable in most countries, that shouldn't be a property it should be an investment, those who see bitcoin as property should learn more or read more about bitcoin and how it works.
To me, bitcoin is an investment and also a treasure, I don't know if am wrong or right.
But if someone may ask you, what do you call BITCOIN?
Your question is kind of funny, because if I may ask, please, What is the difference between a property, an investment, and a treasure? Because if you could analyze them all you will notice that they almost mean the same thing, since a property is also an investment (e.g house).
However here are some definition
Property is any tangible or intangible thing that is owned by someone.
Investment is an item or asset acquired for the main aim of generating income
Treasure is a quantity of precious metals, or other valuable objects
So, all been said you could notice that Bitcoin has same the characteristic as any of these three, as it is intangible, generate income and has value.