The conventional definition of the spin quantum number is s = ⁠ n / 2 ⁠, where n can be any non-negative integer. Hence the allowed values of s are 0, ⁠ 1 / 2 ⁠, 1, ⁠ 3 / 2 ⁠, 2, etc. The value of s for an elementary particle depends only on the type of particle and cannot be altered in any known way (in contrast to the spin direction described below). The spin angular momentum S of any physical system is quantized. The allowed values of S are S = ℏ ℏ s ( s + 1 ) = h 2 π π n 2 ( n + 2 ) 2 = h 4 π π n ( n + 2 ) , where h is the Planck constant, and ℏ ℏ = h 2 π π is the reduced Planck constant. In contrast, orbital angular momentum can only take on integer values of s ; i.e., even-numbered values of n.