Determination of the number of (3686) events taken at BESIII

The number of (3686) events collected by the BESIII detector during the 2021 run period is determined to be (2259. 3 11. 1) 10⁶ by counting inclusive (3686) hadronic events. The uncertainty is systematic and the statistical uncertainty is negligible. Meanwhile, the numbers of (3686) events collected during the 2009 and 2012 run periods are updated to be (107. 70. 6) 10⁶ and (345. 4 2. 6) 10⁶, respectively. Both numbers are consistent with the previous measurements within one standard deviation. The total number of (3686) events in the three data samples is (2712. 414. 3) 10⁶.