621865
Some people advise that all 5s should be rounded up. That is not correct because it introduced an upward bias. In order to leave the results unbiased while retaining reproducibility of calculations, the statistically appropriate procedure is to round 5s so that the previous digit is (or becomes) even. So 821865 should be rounded down.
There is only one whole number in 621860 and that is 621860.
It is 2773049 to the nearest 100.
350
850 to 949
14, which rounds down to 10.
There is only one whole number in 621860 and that is 621860.
621864
4,999 is the greatest whole number.
22999
277299999
It is 2773049 to the nearest 100.
350
94 is the greatest two-digit whole number that when rounded to the nearest ten rounds to a two-digit number.
850 to 949
The greatest whole number would be 499.
749
14, which rounds down to 10.