Engineering Properties of Grains

A bulk grain bed has thermal conductivity $k = 0.15\text{ W/(m}\cdot\text{K)}$, bulk density $\rho = 750\text{ kg/m}^3$, and specific heat $c_p = 2000\text{ J/(kg}\cdot\text{K)}$. Thermal diffusivity $\alpha = \frac{0.15}{1.5 \times 10^6}$ in $\text{m}^2/\text{s}$ is $1.0 \times 10^{-7}$. Expressing $\alpha \times 10^7$ as a dimensionless number, it equals: