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The result must be divisible by 11. 627: 62 − 7 = 55 = 5 × 11. Add 10 times the last digit to the rest. The result must be divisible by 11. (Works because 99 is divisible by 11). 627: 62 + 70 = 132: 13 + 20 = 33 = 3 × 11. If the number of digits is even, add the first and subtract the last digit from the rest. The result must be divisible ...
The least common multiple of the denominators of two fractions is the " lowest common denominator " (lcd), and can be used for adding, subtracting or comparing the fractions. The least common multiple of more than two integers a, b, c, . . . , usually denoted by lcm (a,b,c, . . .), is defined as the smallest positive integer that is divisible ...
Amicable numbers. Amicable numbers are two different natural numbers related in such a way that the sum of the proper divisors of each is equal to the other number. That is, s (a)= b and s (b)= a, where s (n)=σ (n)- n is equal to the sum of positive divisors of n except n itself (see also divisor function). The smallest pair of amicable ...
Division is one of the four basic operations of arithmetic. The other operations are addition, subtraction, and multiplication. What is being divided is called the dividend, which is divided by the divisor, and the result is called the quotient. At an elementary level the division of two natural numbers is, among other possible interpretations ...
12 (twelve) is the natural number following 11 and preceding 13. Twelve is a superior highly composite number , divisible by the numbers from 1 to 4 , and 6 . It is the number of years required for an orbital period of Jupiter .
Digit sums and digital roots can be used for quick divisibility tests: a natural number is divisible by 3 or 9 if and only if its digit sum (or digital root) is divisible by 3 or 9, respectively. For divisibility by 9, this test is called the rule of nines and is the basis of the casting out nines technique for checking calculations.
Wilson's theorem. hide. In algebra and number theory, Wilson's theorem states that a natural number n > 1 is a prime number if and only if the product of all the positive integers less than n is one less than a multiple of n. That is (using the notations of modular arithmetic), the factorial satisfies. exactly when n is a prime number.
{11, 22, 33, 44, 55, 66, 77, 88, 99}. All palindromic numbers with an even number of digits are divisible by 11. [1] There are 90 palindromic numbers with three digits (Using the rule of product: 9 choices for the first digit - which determines the third digit as well - multiplied by 10 choices for the second digit):