Is 81 bmp a safe heart rate? not resting heart rate.

I think so: I think ur asking if a heart rate of 81 when you are not resting (so perhaps after you exercise?) is a safe rate; if that's correct then yes 81 is probably fine. A "normal" heart rate varies depending on lots of things (age, activity, emotions, meds, hydration status, more). In general the better shape you're in, the lower your rate goes. And with vigorous exercise it can go up much higher than 81.

Yes: The maximum heart rate is 220 minus the person's age. The recommendation for moderate intensity exercise is to maintain heart rate at 50-70% of the maximum heart rate.