Electricity from heat is generated by temperature differences. Large differences are much more efficient than small differences and data centers are "small differences" for these purposes.
Unless you can use the heat directly, it won't be worth it to convert it into electricity.
Also important to remember when calculating this for yourself that the temperatures must be represented using an absolute scale (i.e. Kelvins or degrees Rankine).
Unless you can use the heat directly, it won't be worth it to convert it into electricity.