There is no such number because real numbers are infinitely dense. Between any two numbers there are as many real numbers as there are real numbers in total. Counter-intuitive, perhaps, but that is the wonder of infinity.
3.2 is the number that is closest to it. You could not get any closer!
10.025 is the closest number. You could not get any closer!
7 is the closest whole number to 7.03.
The number pi, approximated by 3.1416 is closest to the whole number 3.
3.5 is itself a number and so it is the closest number. You cannot get closer to a number than the number itself!
Numbers are infinitely dense so there can be no "closest". Given any number that claims to be the closest it is always possible to find a number that is closer.
698 is closest to 729.
It is closest to 69.
The closest prime number to 100 is 101.
Number 2 is closest to the Pyrenees Mountains.
The square root of 240 is irrational; the closest number depends upon how many decimal places you want. If you want the closest whole number then: √240 = 15.49193... → closest whole number is 15.
I do not know if it is the closest one, but Clarion Congress hotel is quite close - 1 metro stop.