Well, sure, but people unfamiliar with genetics wouldn't necessarily describe it that way. ;)
From the Akallabêth:
This was the beginning of that people that in the Grey-elven speech are called the Dúnedain: the Númenóreans, Kings among Men. But they did not thus escape from the doom of death that Ilúvatar had set upon all Mankind, and they were mortal still, though their years were long, and they knew no sickness, ere the shadow fell upon them. Therefore they grew wise and glorious, and in all things more like to the Firstborn than any other of the kindreds of Men; and they were tall, taller than the tallest of the sons of Middle-earth; and the light of their eyes was like the bright stars. But their numbers increased only slowly in the land, for though daughters and sons were born to them, fairer than their fathers, yet their children were few.
continued...
Now Elros and Elrond his brother were descended from the Three Houses of the Edain, but in part also both from the Eldar and the Maiar; for Idril of Gondolin and Lúthien daughter of Melian were their fore-mothers. The Valar indeed may not withdraw the gift of death, which comes to Men from Ilúvatar, but in the matter of the Half-elven Ilúvatar gave to them the judgement; and they judged that to the sons of Eärendil should be given choice of their own destiny. And Elrond chose to remain with the Firstborn, and to him the life of the Firstborn was granted. But to Elros, who chose to be a king of Men, still a great span of years was allotted, many times that of the Men of Middle-earth; and all his line, the kings and lords of the royal house, had long life even according to the measure of the Númenóreans. But Elros lived five hundred years, and ruled the Númenóreans four hundred years and ten.
I take that to mean that while the people of Númenór had long life spans, the Kings of Númenór had even longer life spans that that. Whether that is a gift of genetics or a gift of the Valar is a discussion for another forum, I think. ;)