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  2. Perfect digit-to-digit invariant - Wikipedia

    en.wikipedia.org/wiki/Perfect_digit-to-digit...

    The following program in Python determines whether an integer number is a Munchausen Number / Perfect Digit to Digit Invariant or not, following the convention =. num = int ( input ( "Enter number:" )) temp = num s = 0.0 while num > 0 : digit = num % 10 num //= 10 s += pow ( digit , digit ) if s == temp : print ( "Munchausen Number" ) else ...

  3. Perfect number - Wikipedia

    en.wikipedia.org/wiki/Perfect_number

    In number theory, a perfect number is a positive integer that is equal to the sum of its positive proper divisors, that is, divisors excluding the number itself. For instance, 6 has proper divisors 1, 2 and 3, and 1 + 2 + 3 = 6, so 6 is a perfect number. The next perfect number is 28, since 1 + 2 + 4 + 7 + 14 = 28.

  4. Kaprekar's routine - Wikipedia

    en.wikipedia.org/wiki/Kaprekar's_routine

    In number theory, Kaprekar's routine is an iterative algorithm named after its inventor, Indian mathematician D. R. Kaprekar. Each iteration starts with a number, sorts the digits into descending and ascending order, and calculates the difference between the two new numbers. As an example, starting with the number 8991 in base 10: 9981 – 1899 ...

  5. List of Mersenne primes and perfect numbers - Wikipedia

    en.wikipedia.org/wiki/List_of_Mersenne_primes...

    So, 6 is a perfect number because the proper divisors of 6 are 1, 2, and 3, and 1 + 2 + 3 = 6. [2] [4] There is a one-to-one correspondence between the Mersenne primes and the even perfect numbers, but it is unknown whether there exist odd perfect numbers. This is due to the Euclid–Euler theorem, partially proved by Euclid and completed by ...

  6. Binary Golay code - Wikipedia

    en.wikipedia.org/wiki/Binary_Golay_code

    The binary Golay code, G 23 is a perfect code. That is, the spheres of radius three around code words form a partition of the vector space. G 23 is a 12-dimensional subspace of the space F 23 2. The automorphism group of the perfect binary Golay code G 23 (meaning the subgroup of the group S 23 of permutations of the coordinates of F 23

  7. Happy number - Wikipedia

    en.wikipedia.org/wiki/Happy_number

    The examples below implement the perfect digital invariant function for = and a default base = described in the definition of happy given at the top of this article, repeatedly; after each time, they check for both halt conditions: reaching 1, and repeating a number. A simple test in Python to check if a number is happy:

  8. Perfect digital invariant - Wikipedia

    en.wikipedia.org/wiki/Perfect_digital_invariant

    and are trivial perfect digital invariants for all and , all other perfect digital invariants are nontrivial perfect digital invariants. For example, the number 4150 in base b = 10 {\displaystyle b=10} is a perfect digital invariant with p = 5 {\displaystyle p=5} , because 4150 = 4 5 + 1 5 + 5 5 + 0 5 {\displaystyle 4150=4^{5}+1^{5}+5^{5}+0^{5}} .

  9. Narcissistic number - Wikipedia

    en.wikipedia.org/wiki/Narcissistic_number

    In number theory, a narcissistic number [1] [2] (also known as a pluperfect digital invariant (PPDI), [3] an Armstrong number [4] (after Michael F. Armstrong) [5] or a plus perfect number) [6] in a given number base is a number that is the sum of its own digits each raised to the power of the number of digits.