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  2. Table of prime factors - Wikipedia

    en.wikipedia.org/wiki/Table_of_prime_factors

    An economical number has been defined as a frugal number, but also as a number that is either frugal or equidigital. gcd( m , n ) ( greatest common divisor of m and n ) is the product of all prime factors which are both in m and n (with the smallest multiplicity for m and n ).

  3. Greatest common divisor - Wikipedia

    en.wikipedia.org/wiki/Greatest_common_divisor

    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.

  4. List of integer sequences - Wikipedia

    en.wikipedia.org/wiki/List_of_integer_sequences

    2, 8, 20, 28, 50, 82, 126, ... A number of nucleons (either protons or neutrons) such that they are arranged into complete shells within the atomic nucleus. A018226: Superperfect numbers: 2, 4, 16, 64, 4096, 65536, 262144, 1073741824, 1152921504606846976, 309485009821345068724781056, ... Positive integers n for which σ 2 (n) = σ(σ(n)) = 2n ...

  5. Highly composite number - Wikipedia

    en.wikipedia.org/wiki/Highly_composite_number

    A highly composite number is a positive integer that has more divisors than all smaller positive integers. If d(n) denotes the number of divisors of a positive integer n, then a positive integer N is highly composite if d(N) > d(n) for all n < N. For example, 6 is highly composite because d(6)=4 and d(n)=1,2,2,3,2 for n=1,2,3,4,5 respectively.

  6. Superior highly composite number - Wikipedia

    en.wikipedia.org/wiki/Superior_highly_composite...

    8 5040: 2 4 ⋅ 3 2 ⋅ 5 ⋅ 7 : 4,2,1,1 60 2 2 ⋅ 6 ... 120 is another superior highly composite number because it has the highest ratio of divisors to itself ...

  7. Magic number (physics) - Wikipedia

    en.wikipedia.org/wiki/Magic_number_(physics)

    An example is calcium-40, with 20 neutrons and 20 protons, which is the heaviest stable isotope made of the same number of protons and neutrons. Both calcium-48 and nickel-48 are doubly magic because calcium-48 has 20 protons and 28 neutrons while nickel-48 has 28 protons and 20 neutrons. Calcium-48 is very neutron-rich for such a relatively ...

  8. Eddington number - Wikipedia

    en.wikipedia.org/wiki/Eddington_number

    He related α to the Eddington number, which was his estimate of the number of protons in the universe. [2] This led him in 1929 to conjecture that α was exactly 1/136. [3] He devised a "proof" that N Edd = 136 × 2 256, or about 1.57 × 10 79. Other physicists did not adopt this conjecture and did not accept his argument.

  9. Least common multiple - Wikipedia

    en.wikipedia.org/wiki/Least_common_multiple

    Here, the composite number 90 is made up of one atom of the prime number 2, two atoms of the prime number 3, and one atom of the prime number 5. This fact can be used to find the lcm of a set of numbers. Example: lcm(8,9,21) Factor each number and express it as a product of prime number powers.