Girish Mahajan (Editor)

78 (number)

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78
  
79 →

Ordinal
  
78th(seventy-eighth)

Roman numeral
  
LXXVIII

Cardinal
  
seventy-eight

Factorization
  
2 × 3 × 13

Divisors
  
1, 2, 3, 6, 13, 26, 39, 78

78 (seventy-eight) is the natural number following 77 and followed by 79.

Contents

In mathematics

78 is:

  • the dimension of the exceptional Lie group E6 and several related objects.
  • a sphenic number, having 3 distinct prime factors.
  • an abundant number with an aliquot sum of 90.
  • a semiperfect number, as a multiple of a perfect number.
  • the 12th triangular number.
  • a palindromic number in bases 5 (3035), 7 (1417), 12 (6612), 25 (3325) and 38 (2238).
  • a Harshad number in bases 3, 4, 5, 6, 7, 13 and 14.
  • an Erdős–Woods number, since it is possible to find sequences of 78 consecutive integers such that each inner member shares a factor with either the first or the last member.

    • 77 and 78 form a Ruth-Aaron pair.

    In science

  • The atomic number of platinum.

    • In other fields

    78 is also:

  • In reference to gramophone records, 78 refers those meant to be spun at 78 revolutions per minute. Compare: LP,  33 1⁄3 and 45 rpm. 33 + 45 = 78
  • A typical tarot deck containing the 21 trump cards, the Fool and the 56 suit cards make up 78 cards
  • The total number of gifts in the song The Twelve Days of Christmas (since 78 is the 12th triangular number)
  • The Rule of 78s is a method of yearly interest calculation
  • Municipal Okrug 78, a municipal okrug of Tsentralny District of St. Petersburg, Russia
  • NASCAR driver Martin Truex Jr. currently drives the No. 78 Toyota Camry in the NASCAR Sprint Cup Series.

    • References

    78 (number) Wikipedia
    (Text) CC BY-SA


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