I don't know about in the world, but there are approximately 325.4 million people in the U.S. with an active cell phone. https://www.consumeraffairs.com/cell_ph

I don't know about in the world, but there are approximately 325.4 million people in the U.S. with an active cell phone. https://www.consumeraffairs.com/cell_phones/how-many-americans-own-a-smartphone.html https://www.consumeraffairs.com/cell_phones/how-many-america... Of those, approximately 309 million (95%) own a smartphone. https://www.consumeraffairs.com/cell_phones/how-many-americans-own-a-smartphone.html https://www.consumeraffairs.com/cell_phones/how-many-america... Any remaining gap is filled by a single year worth of iPad sales; or filled by just U.S. DoD-issued X.509 certificate cards. It's shocking to me how many people are vastly underestimating how many biometric devices and smart tokens are in existence.