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An economical number has been defined as a frugal number, but also as a number that is either frugal or equidigital. gcd( m , n ) ( greatest common divisor of m and n ) is the product of all prime factors which are both in m and n (with the smallest multiplicity for m and n ).
a superior highly composite number has a ratio between its number of divisors and itself raised to some ... 16, 18, 24, 32, 36, 48, 64, 72, 96, 144, 192, 288, 576 21 ...
For example, 15 is a composite number because 15 = 3 · 5, but 7 is a prime number because it cannot be decomposed in this way. If one of the factors is composite, it can in turn be written as a product of smaller factors, for example 60 = 3 · 20 = 3 · (5 · 4).
In mathematics, a prime power is a positive integer which is a positive integer power of a single prime number. For example: 7 = 7 1, 9 = 3 2 and 64 = 2 6 are prime powers, while 6 = 2 × 3, 12 = 2 2 × 3 and 36 = 6 2 = 2 2 × 3 2 are not. The sequence of prime powers begins:
In number theory, an abundant number or excessive number is a positive integer for which the sum of its proper divisors is greater than the number. The integer 12 is the first abundant number. The integer 12 is the first abundant number.
It follows that arbitrarily large prime numbers can be found as the prime factors of the numbers !, leading to a proof of Euclid's theorem that the number of primes is infinite. [35] When n ! ± 1 {\displaystyle n!\pm 1} is itself prime it is called a factorial prime ; [ 36 ] relatedly, Brocard's problem , also posed by Srinivasa Ramanujan ...
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where n > 1 is an integer and p, q, r are prime numbers, then 2 n × p × q and 2 n × r are a pair of amicable numbers. This formula gives the pairs (220, 284) for n = 2, (17296, 18416) for n = 4, and (9363584, 9437056) for n = 7, but no other such pairs are known. Numbers of the form 3 × 2 n − 1 are known as Thabit numbers.