According to Wien's displacement law, the wavelength $\left(\lambda_{m}\right)$ corresponding to which the energy emitted by a black body maximum is inversely proportional to its absolute temperature $(T)$.
i.e., $\lambda_{m} \propto \frac{1}{T}$
$\Rightarrow \lambda_{m}=\frac{b}{T}$
[where, $b=$ Wien's constant]
$\lambda_{m} \cdot T=b$