Imich achieved the rare feat after the death of Italy's Arturo Licata on April 24. He is five years younger than Misao Okawa, the world's oldest woman.
Before living into his second century, Imich was famous as a researcher of paranormal psychology. He is a fan of spoon-bending magician Uri Geller and in 2002 proposed "a new Nobel Prize" for fields like astronomy and philosophy. He has lived in New York City since the death of his wife in 1986.
Like previous holders of the title, Imich credited "good genes" and exercise for his long life. The fact that he has no children, he has said, also plays a role.
Still, though, he declines to give specific longevity advice.
"I don't know," he told NBC New York, when asked how he had managed to become the world's oldest man. "I simply didn't die earlier."
He added: "I have no idea how this happened."