Dental formula of adult dentition in human beings is represented as $\frac{2123}{2123}$. The number ‘3’ in the numerator part of the formula represents the number of 

The numerator part of a dental formula indicates the number of different types of teeth on one half of the upper jaw (in the order: incisors, canines, premolars and molars). The denominator part indicates the number of different types of teeth on one half of the lower jaw, in same the order.