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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.
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.
For example: automobile car This template should not be used to tag redirects that are taxonomic synonyms . For taxonomic synonyms use {{ R from alternative scientific name }} instead .
A number that is non-palindromic in all bases b in the range 2 ≤ b ≤ n − 2 can be called a strictly non-palindromic number. For example, the number 6 is written as "110" in base 2, "20" in base 3, and "12" in base 4, none of which are palindromes. All strictly non-palindromic numbers larger than 6 are prime.
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
It is the only known example of x 2 +x+1 = y 3, in this case, x=18, ... [56] the next such composite number is 2935561623745, Armstrong number since 3 3 + 7 3 + 1 3 ...
An example spangram with corresponding theme words: PEAR, FRUIT, BANANA, APPLE, etc. Need a hint? Find non-theme words to get hints. For every 3 non-theme words you find, you earn a hint.
Given a set of functional dependencies , an Armstrong relation is a relation which satisfies all the functional dependencies in the closure + and only those dependencies. . Unfortunately, the minimum-size Armstrong relation for a given set of dependencies can have a size which is an exponential function of the number of attributes in the dependencies conside