A quantum number is any of four numbers used to classify electrons and their atomic states. The quantum numbers are as follows:
Azimuthal quantum number, l (= 0, 1, 2, ..., n-1), which denotes the angular momentum and shape of an orbital. Azimuthal quantum numbers 0, 1, 2, and 3 correspond with the s, p, d, and f orbitals, respectively.
Magnetic quantum number, m (= -l, -l+1, ... 0, ... l-1, l), which denotes the orientation of an orbital.
Spin quantum number, s (= ± ½).