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A number n that has more divisors than any x < n is a highly composite number (though the first two such numbers are 1 and 2). Composite numbers have also been called "rectangular numbers", but that name can also refer to the pronic numbers, numbers that are the product of two consecutive integers. Yet another way to classify composite numbers ...
Such a number is algebraic and can be expressed as the sum of a rational number and the square root of a rational number. Constructible number: A number representing a length that can be constructed using a compass and straightedge. Constructible numbers form a subfield of the field of algebraic numbers, and include the quadratic surds.
Highly composite numbers greater than 6 are also abundant numbers. One need only look at the three largest proper divisors of a particular highly composite number to ascertain this fact. It is false that all highly composite numbers are also Harshad numbers in base 10. The first highly composite number that is not a Harshad number is ...
The numbers that end with other digits are all composite: decimal numbers that end in 0, 2, 4, 6, or 8 are even, and decimal numbers that end in 0 or 5 are divisible by 5. [ 11 ] The set of all primes is sometimes denoted by P {\displaystyle \mathbf {P} } (a boldface capital P) [ 12 ] or by P {\displaystyle \mathbb {P} } (a blackboard bold ...
Base systems corresponding to primorials (such as base 30, not to be confused with the primorial number system) have a lower proportion of repeating fractions than any smaller base. Every primorial is a sparsely totient number. [10] The n-compositorial of a composite number n is the product of all composite numbers up to and including n. [11]
A composite number n is a strong pseudoprime to at most one quarter of all bases below n; [3] [4] thus, there are no "strong Carmichael numbers", numbers that are strong pseudoprimes to all bases. Thus given a random base, the probability that a number is a strong pseudoprime to that base is less than 1/4, forming the basis of the widely used ...
1729 is composite, the squarefree product of three prime numbers 7 × 13 × 19. [1] It has as factors 1, 7, 13, 19, 91, 133, 247, and 1729. [2] It is the third Carmichael number, [3] and the first Chernick–Carmichael number. [a] Furthermore, it is the first in the family of absolute Euler pseudoprimes, a subset of Carmichael numbers.
Ω(n), the prime omega function, is the number of prime factors of n counted with multiplicity (so it is the sum of all prime factor multiplicities). A prime number has Ω(n) = 1. The first: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37 (sequence A000040 in the OEIS). There are many special types of prime numbers. A composite number has Ω(n) > 1.