Answer :

1,000,000/70=approx 142857 mins
142857/60=approx 2381 hours
2381/24=approx 99 days
If you want the answer more precisely then do the same calculations but use the exact value each time
(70 beats per minute) x (number of minutes) = (1 million beats)

1 million beats/70 beats per minute = 14285.7142857 minutes.