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Related concepts (42)
Chen prime
In mathematics, a prime number p is called a Chen prime if p + 2 is either a prime or a product of two primes (also called a semiprime). The even number 2p + 2 therefore satisfies Chen's theorem. The Chen primes are named after Chen Jingrun, who proved in 1966 that there are infinitely many such primes. This result would also follow from the truth of the twin prime conjecture as the lower member of a pair of twin primes is by definition a Chen prime. The first few Chen primes are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 47, 53, 59, 67, 71, 83, 89, 101, .
Pierpont prime
In number theory, a Pierpont prime is a prime number of the form for some nonnegative integers u and v. That is, they are the prime numbers p for which p − 1 is 3-smooth. They are named after the mathematician James Pierpont, who used them to characterize the regular polygons that can be constructed using conic sections. The same characterization applies to polygons that can be constructed using ruler, compass, and angle trisector, or using paper folding. Except for 2 and the Fermat primes, every Pierpont prime must be 1 modulo 6.
Hindu–Arabic numeral system
The Hindu–Arabic numeral system or Indo-Arabic numeral system (also called the Hindu numeral system or Arabic numeral system) is a positional decimal numeral system, and is the most common system for the symbolic representation of numbers in the world. It was invented between the 1st and 4th centuries by Indian mathematicians. The system was adopted in Arabic mathematics by the 9th century. It became more widely known through the writings of the Persian mathematician Al-Khwārizmī (On the Calculation with Hindu Numerals, 825) and Arab mathematician Al-Kindi (On the Use of the Hindu Numerals, 830).
70 (number)
70 (seventy) is the natural number following 69 and preceding 71. 70 is: a sphenic number because its factors are 3 distinct primes. a Pell number. the seventh pentagonal number. the fourth tridecagonal number. the fifth pentatope number. the number of ways to choose 4 objects out of 8 if order does not matter. This makes it a central binomial coefficient. the smallest weird number, a natural number that is abundant but not semiperfect. a palindromic number in bases 9 (779), 13 (5513) and 34 (2234).
24 (number)
24 (twenty-four) is the natural number following 23 and preceding 25. 24 is an even composite number, with 2 and 3 as its distinct prime factors. It is the first number of the form 2^qq, where q is an odd prime. It is the smallest number with at least eight positive divisors: 1, 2, 3, 4, 6, 8, 12, and 24; thus, it is a highly composite number, having more divisors than any smaller number. Furthermore, it is an abundant number, since the sum of its proper divisors (36) is greater than itself, as well as a superabundant number.
23 (number)
23 (twenty-three) is the natural number following 22 and preceding 24. Twenty-three is the ninth prime number, the smallest odd prime that is not a twin prime. It is, however, a cousin prime with 19, and a sexy prime with 17 and 29; while also being the largest member of the first prime sextuplet (7, 11, 13, 17, 19, 23). Twenty-three is also the fifth factorial prime, the second Woodall prime, and a happy number in decimal.
25 (number)
25 (twenty-five) is the natural number following 24 and preceding 26. It is a square number, being 52 = 5 × 5, and hence the third non-unitary square prime of the form p2. It is one of two two-digit numbers whose square and higher powers of the number also ends in the same last two digits, e.g., 252 = 625; the other is 76. Twenty five has an even aliquot sum of 6, which is itself the first even and perfect number root of an aliquot sequence; not ending in (1 and 0).
13 (number)
13 (thirteen) is the natural number following 12 and preceding 14. Strikingly folkloric aspects of the number 13 have been noted in various cultures around the world: one theory is that this is due to the cultures employing lunar-solar calendars (there are approximately 12.41 lunations per solar year, and hence 12 "true months" plus a smaller, and often portentous, thirteenth month). This can be witnessed, for example, in the "Twelve Days of Christmas" of Western European tradition. The number 13 is the sixth prime number.
100
100 or one hundred (Roman numeral: C) is the natural number following 99 and preceding 101. In medieval contexts, it may be described as the short hundred or five score in order to differentiate the English and Germanic use of "hundred" to describe the long hundred of six score or 120. 100 is the square of 10 (in scientific notation it is written as 102). The standard SI prefix for a hundred is "hecto-". 100 is the basis of percentages (per cent meaning "per hundred" in Latin), with 100% being a full amount.
127 (number)
127 (one hundred [and] twenty-seven') is the natural number following 126 and preceding 128. It is also a prime number. As a Mersenne prime, 127 is related to the perfect number 8128. 127 is also the largest known Mersenne prime exponent for a Mersenne number, , which is also a Mersenne prime. It was discovered by Édouard Lucas in 1876 and held the record for the largest known prime for 75 years. is the largest prime ever discovered by hand calculations as well as the largest known double Mersenne prime.