Narmacil I sat on the throne of Gondor for sixty-eight years, but for fifty-four of these years Minalcar ruled Gondor as Regent. Narmacil died childless, and was succeeded by his younger brother Calmacil.
The date of Narmacil's birth appears only in The History of Middle-earth volume 12, The Peoples of Middle-earth. It cannot therefore be considered completely reliable.
The root-word nar literally means 'fire' or 'flame', but it is often used figuratively to refer to the sun or to the colour red. So, 'sun sword' or 'red sword' would be reasonable alternative translations.