That rounds to zero.
21 rounded to the nearest hundred is zero. -- The even hundred above 21 is 100. -- The even hundred below 21 is zero. -- 21 is closer to the lower one than it is to the higher one.
Oh, dude, rounding 21 to the nearest hundred? That's like asking me to find a unicorn in a haystack. But hey, technically speaking, when you round 21 to the nearest hundred, it stays as 21. It's like trying to make a penny into a dollar - just not gonna happen.
21 to the nearest tenths is 21.0
20.663 to nearest whole number is 21
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.