4600
The least number is 4550; the greatest is 4650 and I have no idea what a phone number has to do with any of this.
100
That is 4800
4198 to the nearest 100 = 4200
100
100
100
853 rounded to the nearest 100: 900. 10853 rounded to the nearest 100: 10900.
2500 is already at the nearest 100.
599 to the nearest 100 is 600.
6,287 to the nearest 100 is 6,300.