Infinitely many. It depends on the accuracy to which the numbers were given prior to rounding.
It is 600000.
600000
0
Infinitely many.
There are infinitely many such numbers.
550000 to 649999
600000
It is 600000.
It is 600000.
It is 600000.
It is 600000.
It is 600000.
It is 600000.
It is 600000.
It is 600000.
600000
It is 600000.