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First, the digits of the number being tested are grouped in blocks of three. The odd numbered groups are summed. The sum of the even numbered groups is then subtracted from the sum of the odd numbered groups. The test number is divisible by 7, 11 or 13 iff the result of the summation is divisible by 7, 11 or 13 respectively. [2] [3] Example:
Additionally, since the smallest four primes (2, 3, 5, 7) are either divisors or neighbors of 6, senary has simple divisibility tests for many numbers. Furthermore, all even perfect numbers besides 6 have 44 as the final two digits when expressed in senary, which is proven by the fact that every even perfect number is of the form 2 p – 1 (2 p ...
Such method is 6.7% more efficient than MIME-64 which encodes a 24 bit number into 4 printable characters. 89: Largest base for which all left-truncatable primes are known. 90: Nonagesimal: Related to Goormaghtigh conjecture for the generalized repunit numbers (111 in base 90 = 1111111111111 in base 2). 95: Number of printable ASCII characters ...
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, ... The prime numbers p n , with n ≥ 1 . A prime number is a natural number greater than 1 that is not a product of two smaller natural numbers.
6 to 8 digits 22: 9: 2degrees: 7 digits 24? Unused: Protected by Management Committee on 30 January 2009 to preserve the potential code expansion option. 25: 8-9: Unused: 6-7 digits - Was used by Telecom New Zealand (now called Spark) until it was shut down on 31 March 2007. All numbers have now migrated to 027 (7-digit) and 0274 (6-digit).
A list of articles about numbers (not about numerals). Topics include powers of ten, notable integers, prime and cardinal numbers, and the myriad system.
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For example, to find the seventh Fortunate number, one would first calculate the product of the first seven primes (2, 3, 5, 7, 11, 13 and 17), which is 510510. Adding 2 to that gives another even number, while adding 3 would give another multiple of 3. One would similarly rule out the integers up to 18.