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Al-Khalil ibn Ahmad al-Farahidi: wrote a (now lost) book on cryptography titled the "Book of Cryptographic Messages". Al-Kindi, 9th century Arabic polymath and originator of frequency analysis. Athanasius Kircher, attempts to decipher crypted messages; Augustus the Younger, Duke of Brunswick-Lüneburg, wrote a standard book on cryptography
Carl Bernard Pomerance (born 1944 in Joplin, Missouri) is an American number theorist.He attended college at Brown University and later received his Ph.D. from Harvard University in 1972 with a dissertation proving that any odd perfect number has at least seven distinct prime factors. [1]
So, 6 is a perfect number because the proper divisors of 6 are 1, 2, and 3, and 1 + 2 + 3 = 6. [2] [4] Euclid proved c. 300 BCE that every prime expressed as M p = 2 p − 1 has a corresponding perfect number M p × (M p +1)/2 = 2 p − 1 × (2 p − 1). For example, the Mersenne prime 2 2 − 1 = 3 leads to the corresponding perfect number 2 2 ...
This is a list of topics in number theory. See also: List of recreational number theory topics; Topics in cryptography; Divisibility ... Almost perfect number;
In number theory, a perfect number is a positive integer that is equal to the sum of its positive proper divisors, that is, divisors excluding the number itself. For instance, 6 has proper divisors 1, 2 and 3, and 1 + 2 + 3 = 6, so 6 is a perfect number. The next perfect number is 28, since 1 + 2 + 4 + 7 + 14 = 28.
The Fortune 500 list of companies includes only publicly traded companies, also including tax inversion companies. There are also corporations having foundation in the United States, such as corporate headquarters, operational headquarters and independent subsidiaries. The list excludes large privately held companies such as Cargill and Koch ...
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The company released version 9 of the software in 2005. PGP Corporation's focus shifted towards the corporate market. [5] In 2004, the company announced plans to integrate with Symantec anti-virus technology. [6] In 2009, Callas left to be a security consultant. [7]