SB 3.11.24
svam svam kalam manur bhunkte
sadhikam hy eka-saptatim
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Each and every Manu enjoys a life of a little more than seventy-one sets of four millenniums.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The duration of life of a Manu comprises seventy-one sets of four millenniums, as described in the Visnu Purana. The duration of life of one Manu is about 852,000 years in the calculation of the demigods, or, in the calculation of human beings, 306,720,000 years.