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  2. Perfect totient number - Wikipedia

    en.wikipedia.org/wiki/Perfect_totient_number

    In number theory, a perfect totient number is an integer that is equal to the sum of its iterated totients.That is, one applies the totient function to a number n, apply it again to the resulting totient, and so on, until the number 1 is reached, and adds together the resulting sequence of numbers; if the sum equals n, then n is a perfect totient number.

  3. Euler's totient function - Wikipedia

    en.wikipedia.org/wiki/Euler's_totient_function

    A perfect totient number is an integer that is equal to the sum of its iterated totients. That is, we apply the totient function to a number n, apply it again to the resulting totient, and so on, until the number 1 is reached, and add together the resulting sequence of numbers; if the sum equals n, then n is a perfect totient number.

  4. 183 (number) - Wikipedia

    en.wikipedia.org/wiki/183_(number)

    183 is a perfect totient number, a number that is equal to the sum of its iterated totients. [ 1 ] Because 183 = 13 2 + 13 + 1 {\displaystyle 183=13^{2}+13+1} , it is the number of points in a projective plane over the finite field Z 13 {\displaystyle \mathbb {Z} _{13}} .

  5. 39 (number) - Wikipedia

    en.wikipedia.org/wiki/39_(number)

    It is a perfect totient number. [3] 39 is the sum of five consecutive primes (3 + 5 + 7 + 11 + 13) and also is the product of the first and the last of those ...

  6. 255 (number) - Wikipedia

    en.wikipedia.org/wiki/255_(number)

    It is a perfect totient number, the smallest such number to be neither a power of three nor thrice a prime. Since 255 is the product of the first three Fermat primes, the regular 255-gon is constructible. In base 10, it is a self number. 255 is a repdigit in base 2 (11111111), in base 4 (3333), and in base 16 (FF).

  7. 81 (number) - Wikipedia

    en.wikipedia.org/wiki/81_(number)

    The number of stanzas or chapters in the Tao Te Ching (in the most common arrangements). The number of provinces in Turkey. The number of prayers said in the Rosary in each night. "The 81" is a 1965 song by Candy and the Kisses. [importance?] Artemis 81 is a 1981 BBC TV science fiction drama. [9] 'The Eighty-One Brothers' is a Japanese fable [10]

  8. Cyclic number (group theory) - Wikipedia

    en.wikipedia.org/wiki/Cyclic_number_(group_theory)

    A cyclic number [1] [2] is a natural number n such that n and φ(n) are coprime. Here φ is Euler's totient function. An equivalent definition is that a number n is cyclic if and only if any group of order n is cyclic. [3] Any prime number is clearly cyclic. All cyclic numbers are square-free. [4] Let n = p 1 p 2 …

  9. 72 (number) - Wikipedia

    en.wikipedia.org/wiki/72_(number)

    144, or twice 72, is also highly totient, as is 576, the square of 24. [8] While 17 different integers have a totient value of 72, the sum of Euler's totient function φ(x) over the first 15 integers is 72. [9] It also is a perfect indexed Harshad number in decimal (twenty-eighth), as it is divisible by the sum of its digits . [10]