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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.
In number theory, a factorion in a given number base is a natural number that equals the sum of the factorials of its digits. [1] [2] [3] The name factorion was coined by the author Clifford A. Pickover. [4]
This is a list of recreational number theory topics (see number theory, recreational mathematics). Listing here is not pejorative : many famous topics in number theory have origins in challenging problems posed purely for their own sake.
The number 4 can also represent the four sacred directions: north, south, east, and west, Widney explains. This reminds us that “we are all connected and need to respect and care for others to ...
The smallest friendly number is 6, forming for example, the friendly pair 6 and 28 with abundancy σ(6) / 6 = (1+2+3+6) / 6 = 2, the same as σ(28) / 28 = (1+2+4+7+14+28) / 28 = 2. The shared value 2 is an integer in this case but not in many other cases. Numbers with abundancy 2 are also known as perfect numbers. There are several unsolved ...
A list of articles about numbers (not about numerals). Topics include powers of ten, notable integers, prime and cardinal numbers, and the myriad system.
These examples shouldn't have links, since they are base 3 and 4 numbers but the links are to base 10 numbers and so are meaningless --206.171.6.11 15:12, 8 November 2006 (UTC) Some base three Armstrong numbers are: 0,1,2,12,122; Some base four Armstrong numbers are: 0,1,2,3,313
A trimorphic number or spherical number occurs when the polynomial function is () =. [1] All automorphic numbers are trimorphic. The terms circular and spherical were formerly used for the slightly different case of a number whose powers all have the same last digit as the number itself.