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6174. The number 6174 is known as Kaprekar's constant [1] [2] [3] after the Indian mathematician D. R. Kaprekar. This number is renowned for the following rule: Take any four-digit number, using at least two different digits (leading zeros are allowed). Arrange the digits in descending and then in ascending order to get two four-digit numbers ...
Luhn algorithm. The Luhn algorithm or Luhn formula, also known as the " modulus 10" or "mod 10" algorithm, named after its creator, IBM scientist Hans Peter Luhn, is a simple check digit formula used to validate a variety of identification numbers. It is described in U.S. Patent No. 2,950,048, granted on August 23, 1960.
As a result, 4 does not impact the number of significant figures or digits in the result of calculations with it. A mathematical or physical constant has significant figures to its known digits. π is a specific real number with several equivalent definitions. All of the digits in its exact decimal expansion 3.14159265358979323... are significant.
Repeating decimal. A repeating decimal or recurring decimal is a decimal representation of a number whose digits are eventually periodic (that is, after some place, the same sequence of digits is repeated forever); if this sequence consists only of zeros (that is if there is only a finite number of nonzero digits), the decimal is said to be ...
4-Digits. 4-Digits (abbreviation: 4-D) is a lottery in Germany, Singapore, and Malaysia. Individuals play by choosing any number from 0000 to 9999. Then, twenty-three winning numbers are drawn each time. If one of the numbers matches the one that the player has bought, a prize is won.
Four fours. Four fours is a mathematical puzzle, the goal of which is to find the simplest mathematical expression for every whole number from 0 to some maximum, using only common mathematical symbols and the digit four. No other digit is allowed. Most versions of the puzzle require that each expression have exactly four fours, but some ...
Palindromic number. A palindromic number (also known as a numeral palindrome or a numeric palindrome) is a number (such as 16461) that remains the same when its digits are reversed. In other words, it has reflectional symmetry across a vertical axis. The term palindromic is derived from palindrome, which refers to a word (such as rotor or ...
Squares of even numbers are even, and are divisible by 4, since (2n) 2 = 4n 2. Squares of odd numbers are odd, and are congruent to 1 modulo 8, since (2n + 1) 2 = 4n(n + 1) + 1, and n(n + 1) is always even. In other words, all odd square numbers have a remainder of 1 when divided by 8. Every odd perfect square is a centered octagonal number ...