36*37^62

In any, there are up to 36*37^62=609,269,436,886,430,207,415,724,313,935,118,185,567,366,503,082,897,299,581,429,354,820,868,365,318,591,594,476,323,925,066,482,884 possible second-level domain names, but some correspond to illegal contents.