Abstract
A graph G of order n has prime cordial labeling if its vertices can be assigned the distinct labels 1, 2... ,n such that if each edge xy in G is assigned the label 1 in case the labels of x and y are relatively prime and 0 otherwise, then the number of edges labeled with 0 and the number of edges labeled with 1 differ by at most 1. In this paper, we give a complete characterization of complete graphs which are prime cordial and we give a prime cordial labeling of the closed helm H-n, and present a new way of prime cordial labeling of P-n(2) . Finally we make a correction of the proof of Theorem 2.5 in [12].