The number one.
prime number
A negative one.
The phone number of the Carr'S One Of A Kind Museum is: 509-489-8859.
The probability of that one special kind of outcome.
a prime number you indiot
A number that has factors other than itself and one
A composite number.
It is a prime number which has only two factors which are itself and one
it is equal to a whole number
A mixed fraction.
If you mean what kind of element can exist as one atom, the answer is the noble gases in group 18. All elements are composed of one kind of atom, having a unique number of protons, or atomic number.