-1

is the integer between.

Math features

 * is an odd number.
 * -1 is used in false mathematical proofs where -1 = 1.
 * -1 is (not considered to be) a deficient number (although it has the property of an abundant number).
 * The square root of -1, or $$\sqrt{-1}$$, is an imaginary number, known as the imaginary unit, commonly used as i.
 * -1 is not prime, and neither is it composite. (1 has this property)

-&frac12;

 * -$1⁄2$ is half of -1 (see section above for -1)
 * -$1⁄2$ is the only number where $$2n=n-0.5$$, since the -0.5 is in the equation itself.