Calculate the number 5371

After a very busy day, a commuter settled down in her seat and closed her eyes as the train departed London for Liverpool. As the train rolled out of the station, the guy sitting next to her pulled out his mobile phone and started talking in a loud voice: "Hi sweetheart, it's Eric, I'm on the train, I know it's the six thirty and not the four thirty but I had a long meeting, no, honey, not with that floozie from the accounts office, with the boss. No sweetheart, you're the only one in my life, yes, I'm sure, cross my heart."
Fifteen minutes later, he was still talking loudly, when the young woman sitting next to him, who was obviously angered by his continuous rabble, yelled at the top of her voice: "Hey, Eric, turn that stupid phone off and get yourself back into bed!"