Wave number can be defined as the number of waves per unit length. In other words it is number of waves that occurs across a fixed distance. It is also known as propagation constant.
Wavenumber is reciprocal of Wave length. Unit of Wavenumber are cycles per centimeter or inverse centemeters.
Wave number (k) = 2 π / λ (Wave length)
Dimensional formula of wavelength = M0L1T0
So putting this value in the formula we get,
Dimensional Formula of Wave number or Propagation constant = M0L-1T0
SI units of Wave number or Propagation constant is m-1.