Combining with the mating-type peptide pheromone P-factor and transmitting the signal across the membrane to initiate a change in cell activity. P-factor is a polypeptide of 23 residues, with the sequence Thr-Tyr-Ala-Asp-Phe-Leu-Arg-Ala-Tyr-Gln-Ser-Trp-Asn-Thr-Phe-Val-Asn-Pro-Asp-Arg-Pro-Asn-Leu, and is a peptide pheromone released by Schizosaccharomyces pombe cells of the cellular mating type Plus.