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
• Irish:

  Old Irish: áram foirbthe 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 (ru) 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
• Perfect number on Wikipedia.Wikipedia