With respect to the current rate of Bitcoin been valued at $108,000 per BTC at the time of writing this post, then I'm pretty sure that the amount of Bitcoin whose current value gave you $1.8million must have over 16.66 BTC (i.e 1,800,000/108,000 = 16.66 BTC)[/b]. Which also implies you own a whooping 16 Bitcoins at the moment, which is actually crazy, judging by the fact that the amount you bought it 12years ago wasn't even up to $50, and now 12yrs later, you are now a millionaire.
12 years ago the price was approximately 100usd/BTC, therefore the investment sum was around 1500 usd.
And even if we are to accept the price of Bitcoin back then 12years ago to be 100usdt/BTC, of which 16.6 Bitcoin would have been worth 1,660usdt, and for the fact that his investment of 1660usdt 12years ago to be now worth $1.8Million, which is approximately over 109,000% percent of the initial capital, far high than what any other investments in the world will ever offer it's investors in 100years and above. But yet Bitcoin was able to offer such investment of 109,000 percent profit in just 12years. And if I was to be in O.P's shoe, I would have just sold just 3 Bitcoin to establish a daily income generating business, while I keep the remaining 13BTC. But it's obvious, O.P, seems to be a very rich person and don't care.