M-1l-3t4a2

The dimension of permittivity of any medium or vacuum (free space) is C2 N-1 m-2

The absolute permittivity of a medium is its relative permittivity multiplied by the vacuum permittivity.

The absolute permittivity is a proportionality constant between the electric and displacement field with units of Farad/meters (in SI units). This number is usually very small (e.g. for air: 0.000 000 000 008 85 F/m).

The relative permittivity is a unit-less number scaled upward to present nicer numbers (e.g. for air: 1.0005).

To get the absolute permittivity from the relative permittivity one should multiply with the vacuum permittivity: 8.85418781... E-12 F/m.

YES IT IS. Any quantity which is ratio of two physical quantities having same unit is dimensionless. Dielectric constant is ratio of Permittivty of medium to the permittivity of free space. As Permittivity of medium and permittivity of free space both have same units(F/m ie Farad/meter) dielectric constant becomes dimensionless quantity