7129
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 19
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 7130
- Proper Divisor Sum (Aliquot Sum)
- 1
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 7128
- Möbius Function
- -1
- Radical
- 7129
- Omega Function (Ω)
- 1
- Little Omega Function (ω)
- 1
Special
- Factorial
- no
- Catalan Number
- no
- Bell Number
- no
- Motzkin Number
- no
- Primorial
- no
Figurate Numbers
- Fibonacci Number
- no
- Triangular Number
- no
- Perfect Square
- no
- Perfect Cube
- no
- Pentagonal Number
- no
- Hexagonal Number
- no
- Lucas Number
- no
- Tetrahedral Number
- no
- Pell Number
- no
- Tribonacci Number
- no
- Pronic Number
- no
Recreational
- Happy Number
- no
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 119
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- yes
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 914
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Let A(n) = #{(i,j): i^2 + j^2 <= n}, V(n) = Pi*n, P(n) = A(n) - V(n); A000099 gives values of n where |P(n)| sets a new record; sequence gives A(A000099(n)).at n=24A000323
- a(n) = numerator of harmonic number H(n) = Sum_{i=1..n} 1/i.at n=8A001008
- Primes p such that the multiplicative order of 2 modulo p is (p-1)/4.at n=43A001134
- Numerator of the n-th harmonic number H(n) divided by (n+1); a(n) = A001008(n) / ((n+1)*A002805(n)).at n=8A002547
- Smallest number that requires n iterations of the unitary totient function (A047994) to reach 1.at n=20A003271
- Primes p == 1 (mod 8), p = a^2 +64*b^2 such that y^2 = x^3 + p*x has rank 0.at n=35A007765
- a(n) = (1/1 + 1/2 + ... + 1/n)*lcm{1,2,...,n}.at n=8A025529
- Triangle read by rows: square of the lower triangular mean matrix.at n=36A027446
- Primes that are palindromic in base 9.at n=18A029977
- Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted then there are a pair of central terms both equal to 6.at n=25A031419
- Primes of form x^2 + 94*y^2.at n=47A033204
- Numerators of alternating sum transform (PSumSIGN) of Harmonic numbers H(n) = A001008/A002805.at n=17A035048
- Number of partitions of n such that cn(0,5) = cn(1,5) < cn(2,5) = cn(3,5) = cn(4,5).at n=77A036873
- Base-9 palindromes that start with 1.at n=27A043028
- Primes with first digit 7.at n=31A045713
- Primes p for which the period of reciprocal 1/p is (p-1)/12.at n=9A056217
- Absolute value of numerator of non-Euler-constant term of Laurent expansion of Gamma function at s = -n.at n=9A060746
- Primes p such that q-p = 22, where q is the next prime after p.at n=11A061779
- a(n) = p.q in decimal notation where p = prime(n) and q is the smallest prime (A066065(n)) such that the concatenation p.q is a prime.at n=19A066064
- Least m such that card(invphi(phi(m)))=n.at n=33A066420