perfect number

perfect number

English

Etymology

Calque of Latin numerus perfectus, with this use of perfectus itself a semantic loan from Ancient Greek τέλειος (téleios).

Noun

perfect number (plural perfect numbers)

1. (number theory) A number that is the sum of all of its divisors except itself.

   The factors of 6 are 1, 2, 3 and 6, and 1 + 2 + 3 = 6, so 6 is a perfect number.

   The factors of 28 are 1, 2, 4, 7, 14 and 28, and 1 + 2 + 4 + 7 + 14 = 28, so 28 is a perfect number.

Translations

a number that is the sum of all of its divisors except itself

Catalan: nombre perfecte Chinese: Mandarin: 完全數／完全数 (zh) (wánquánshù) Dutch: perfect getal Finnish: täydellinen luku French: nombre parfait (fr) m German: vollkommene Zahl f, perfekte Zahl f, ideale Zahl f Icelandic: fullkomin tala f Italian: numero perfetto (it) m Japanese: 完全数 (かんせんすう; kanzen-su) Latin: numerus perfectus m Norwegian: perfekt tall Portuguese: número perfeito m Romanian: număr perfect (ro) n Russian: соверше́нное число́ n (soveršénnoje čisló) Slovak: dokonalé číslo n Spanish: número perfecto m Swedish: perfekt tal (sv) n Tagalog: himpit na bilang Turkish: mükemmel sayı

See also

• abundant number
• amicable numbers
• deficient number
• Mersenne prime
• sociable numbers
• Wikipedia article on perfect numbers