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Sunspots are temporary spots on the Sun's surface that are darker than the surrounding area. They are one of the most recognizable Solar phenomena and despite the fact that they are mostly visible in the solar photosphere they usually affect the entire solar atmosphere. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection. Sunspots appear within active regions, usually in pairs of opposite magnetic polarity. Their number varies according to the approximately 11-year solar cycle.
In number theory, a prime number p is a Sophie Germain prime if 2p + 1 is also prime. The number 2p + 1 associated with a Sophie Germain prime is called a safe prime. For example, 11 is a Sophie Germain prime and 2 × 11 + 1 = 23 is its associated safe prime. Sophie Germain primes and safe primes have applications in public key cryptography and primality testing. It has been conjectured that there are infinitely many Sophie Germain primes, but this remains unproven.
11 (eleven) is the natural number following 10 and preceding 12. In English, it is the smallest positive integer whose name has three syllables.
111 is the natural number following 110 and preceding 112.
In mathematics, a Cunningham chain is a certain sequence of prime numbers. Cunningham chains are named after mathematician A. J. C. Cunningham. They are also called chains of nearly doubled primes.
23 (twenty-three) is the natural number following 22 and preceding 24.
89 (eighty-nine) is the natural number following 88 and preceding 90.
120 is the natural number following 119 and preceding 121. It is five sixths of a gross, or ten dozens.
1000 or one thousand is the natural number following 999 and preceding 1001. In most English-speaking countries, it can be written with or without a comma or sometimes a period separating the thousands digit: 1,000.
127 is the natural number following 126 and preceding 128. It is also a prime number.
700 is the natural number following 699 and preceding 701.
The interesting number paradox is a humorous paradox which arises from the attempt to classify every natural number as either "interesting" or "uninteresting". The paradox states that every natural number is interesting. The "proof" is by contradiction: if there exists a non-empty set of uninteresting natural numbers, there would be a smallest uninteresting number – but the smallest uninteresting number is itself interesting because it is the smallest uninteresting number, thus producing a contradiction.
The Wolf number is a quantity that measures the number of sunspots and groups of sunspots present on the surface of the Sun. Historically, it was only possible to detect sunspots on the far side of the Sun indirectly using helioseismology. Since 2006, NASA's STEREO spacecrafts allow their direct observation.
139 is the natural number following 138 and preceding 140.
100,000,000 is the natural number following 99,999,999 and preceding 100,000,001.
168 is the natural number following 167 and preceding 169.
In number theory, primes in arithmetic progression are any sequence of at least three prime numbers that are consecutive terms in an arithmetic progression. An example is the sequence of primes, which is given by for .
41 (forty-one) is the natural number following 40 and preceding 42.
In number theory, a bi-twin chain of length k + 1 is a sequence of natural numbers
References
- ↑ Wells, David (1997). The Penguin Dictionary of Curious and Interesting Numbers. Penguin. p. 115. ISBN 9780140261493.
- ↑ Cohen, Theodore J.; Lintz, Paul R. (August 1974). "Long term periodicities in the sunspot cycle". Nature. 250 (5465): 398–400. Bibcode:1974Natur.250..398C. doi:10.1038/250398a0. S2CID 4181720.
