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The greatest common divisor (GCD) of integers a and b, at least one of which is nonzero, is the greatest positive integer d such that d is a divisor of both a and b; that is, there are integers e and f such that a = de and b = df, and d is the largest such integer.
d() is the number of positive divisors of n, including 1 and n itself; σ() is the sum of the positive divisors of n, including 1 and n itselfs() is the sum of the proper divisors of n, including 1 but not n itself; that is, s(n) = σ(n) − n
A number that has the same number of digits as the number of digits in its prime factorization, including exponents but excluding exponents equal to 1. A046758: Extravagant numbers: 4, 6, 8, 9, 12, 18, 20, 22, 24, 26, 28, 30, 33, 34, 36, 38, ... A number that has fewer digits than the number of digits in its prime factorization (including ...
The first: 4, 8, 9, 16, 25, 27, 32, 36, 49, 64, 81, 100 (sequence A001597 in the OEIS). 1 is sometimes included. A powerful number (also called squareful ) has multiplicity above 1 for all prime factors.
For if the algorithm requires N steps, then b is greater than or equal to F N+1 which in turn is greater than or equal to φ N−1, where φ is the golden ratio. Since b ≥ φ N−1, then N − 1 ≤ log φ b. Since log 10 φ > 1/5, (N − 1)/5 < log 10 φ log φ b = log 10 b. Thus, N ≤ 5 log 10 b.
Indeed, in this proposition the exponents are all equal to one, so nothing is said for the general case. While Euclid took the first step on the way to the existence of prime factorization, Kamāl al-Dīn al-Fārisī took the final step [ 8 ] and stated for the first time the fundamental theorem of arithmetic.
A multiple of a number is the product of that number and an integer. For example, 10 is a multiple of 5 because 5 × 2 = 10, so 10 is divisible by 5 and 2. Because 10 is the smallest positive integer that is divisible by both 5 and 2, it is the least common multiple of 5 and 2.
180 is a 61-gonal number, [2] while 61 is the 18th prime number. Half a circle has 180 degrees, [7] and thus a U-turn is also referred to as a 180. Summing Euler's totient function φ(x) over the first + 24 integers gives 180. In binary it is a digitally balanced number, since its binary representation has the same number of zeros as ones ...