If the half life is 24360 years and after 1000 years I have 2.1 gm left, what was the initial qty. Doing it in a common sense way keeps giving me 51gm and that doesn't make sense. formula is y=ae -bt

2.1 = a [1/2^(1000/24360)]

log(2.1) =
log(a) + (1000/24360)log(1/2)

2.1606 ?