^^INTERESTING QUESTION, lets get over analytical on this
0 Can't be lonely, because no one is lonely when there's nothing. So as far as integers go I'd say "1" is the loneliest positive integer.
But what about -1, that's even lonelier. Not only is it just as lonely as 1 in magnitude, but it's negative, which means it has no square root. While the root of 1 is itself, which is pretty lonely, the root of -1 is only IMAGINARY which, I'd say, is even lonelier!
What if "i" the imaginary root of -1 is lonely, I mean it's name is "I" not "We" or "Us", but simply "i" that's pretty lonely (or perhaps self absorbed).
What about fractions? Half is probably lonelier than one, because it's incomplete, it's only a fraction of a whole, it needs something else to make it whole again. That's pretty lonely
But I'd say the loneliest number is ε. ε is a symbol to represent a quality that is "infinitely small". Basically this is a 1, at the end of an infinite 0's, not only is it super lonely, but it's surrounded by nothing, can never be imagined, would need an infinite amount of others to make it whole and it simply is the smallest, most insignificant thing that in a lot of cases it's easy to just simply ignore. So 1 is not the loneliest number, I'd say ε is.
^ No
Don'[t you hate it when you miss a question after a long answer