Verified answer

the answer is 1.9x10^6 but i had to use an ***-backwards way to figure it out. i don't know how to use any formula for this sorry

You could mathematically work out how long it would take to decay down to one atom - in reality though Heisenbergs uncertainty prinicple would come into play - the T1/2 of an element is an average and applies to the element as a whole and not to each individual atom