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  2. 128 (number) - Wikipedia

    en.wikipedia.org/wiki/128_(number)

    The sum of Euler's totient function φ(x) over the first twenty integers is 128. [4] 128 can be expressed by a combination of its digits with mathematical operators, thus 128 = 2 8 − 1, making it a Friedman number in base 10. [5] A hepteract has 128 vertices. 128 is the only 3-digit number that is a 7th power (2 7).

  3. List of Mersenne primes and perfect numbers - Wikipedia

    en.wikipedia.org/wiki/List_of_Mersenne_primes...

    As a result, there is a one-to-one correspondence between Mersenne primes and even perfect numbers, so a list of one can be converted into a list of the other. [ 1 ] [ 5 ] [ 6 ] It is currently an open problem whether there are infinitely many Mersenne primes and even perfect numbers.

  4. Mersenne prime - Wikipedia

    en.wikipedia.org/wiki/Mersenne_prime

    Proof: 2 p+1 ≡ 2 (mod q), so 2 ⁠ 1 / 2 ⁠ (p+1) is a square root of 2 mod q. By quadratic reciprocity, every prime modulus in which the number 2 has a square root is congruent to ±1 (mod 8). A Mersenne prime cannot be a Wieferich prime. Proof: We show if p = 2 m − 1 is a Mersenne prime, then the congruence 2 p−1 ≡ 1 (mod p 2) does ...

  5. Square (algebra) - Wikipedia

    en.wikipedia.org/wiki/Square_(algebra)

    The square of an integer may also be called a square number or a perfect square. In algebra, the operation of squaring is often generalized to polynomials, other expressions, or values in systems of mathematical values other than the numbers. For instance, the square of the linear polynomial x + 1 is the quadratic polynomial (x + 1) 2 = x 2 ...

  6. Square number - Wikipedia

    en.wikipedia.org/wiki/Square_number

    Square number 16 as sum of gnomons. In mathematics, a square number or perfect square is an integer that is the square of an integer; [1] in other words, it is the product of some integer with itself. For example, 9 is a square number, since it equals 3 2 and can be written as 3 × 3.

  7. Square triangular number - Wikipedia

    en.wikipedia.org/wiki/Square_triangular_number

    All square triangular numbers have the form , where is a convergent to the continued fraction expansion of , the square root of 2. [ 4 ] A. V. Sylwester gave a short proof that there are infinitely many square triangular numbers: If the n {\displaystyle n} th triangular number n ( n + 1 ) 2 {\displaystyle {\tfrac {n(n+1)}{2}}} is square, then ...

  8. 8128 - Wikipedia

    en.wikipedia.org/wiki/8128

    8128 is the integer following 8127 and preceding 8129.. It is most notable for being a perfect number (its proper divisors 1, 2, 4, 8, 16, 32, 64, 127, 254, 508, 1016, 2032, and 4064 add up to 8128), and one of the earliest numbers to be recognized as such.

  9. Perfect square - Wikipedia

    en.wikipedia.org/wiki/Perfect_square

    A perfect square is an element of algebraic structure that is equal to the square of another element. Square number, a perfect square integer. Entertainment