100.01, 100.02
1000 numbers. From 19,500 to 20,499 all round to 20,000
1000
950 to 999 would round to 1000 because 949 and less would round to 900.
The prime numbers (factors) of 1000 are: 2 and 5
1000 and 2
999, 1001, and 1,499.999999
It is 1000*(1000+1)/2 = 500500
1000
When rounding to the nearest thousand (1000), half the numbers (1000 ÷ 2 = 500) round up, and the other half round down - except for those which are exactly half-way: they round up. Thus the largest number that will round to 27,000 to the nearest thousand must round down to it and is 27,000 + 500 - 1 = 27,499.
Half of 1000 is 500, so numbers in the range 5000 ± 500 round to 5000 to the nearest 1000 EXCEPT that numbers exactly half way round up. ie numbers greater than or equal to 5000 - 500 = 4500 and less than 5000 + 500 = 5500 will round to 5000 to the nearest 1000. So the largest whole number that rounds to 5000 to the nearest 1000 is 5500 - 1 = 5499.
The prime factors of 1000 are: 2, 5
If you round something to 2, it will be 2. Possible starting points include numbers from 1.5 to 2.4