691
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 16
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 692
- 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
- 690
- Möbius Function
- -1
- Radical
- 691
- 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
- 126
- Smith Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 125
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Names
- German
- sechshunderteinundneunzig· ordinal: sechshunderteinundneunzigste
- English
- six hundred ninety-one· ordinal: six hundred ninety-first
- Spanish
- seiscientos noventa y uno· ordinal: 691º
- French
- six cent quatre-vingt-onze· ordinal: six cent quatre-vingt-onzième
- Italian
- seicentonovantuno· ordinal: 691º
- Latin
- sescenti nonaginta unus· ordinal: 691.
- Portuguese
- seiscentos e noventa e um· ordinal: 691º
Appears in sequences
- Let A(n) = #{(i,j,k): i^2 + j^2 + k^2 <= n}, V(n) = (4/3)*Pi*n^(3/2), P(n) = A(n) - V(n); A000092 gives values of n where |P(n)| sets a new record; sequence gives A(A000092(n)).at n=7A000413
- Number of acyclic quaternary ammonium ions with n carbon atoms.at n=8A000633
- Primes p of the form 3k+1 such that Sum_{x=1..p} cos(2*Pi*x^3/p) > sqrt(p).at n=29A000921
- Irregular primes: primes p such that at least one of the numerators of the Bernoulli numbers B_2, B_4, ..., B_{p-3} (A000367) is divisible by p.at n=46A000928
- Primes with 3 as smallest primitive root.at n=29A001123
- Primes p such that the multiplicative order of 2 modulo p is (p-1)/3.at n=9A001133
- Artiads: the primes p == 1 (mod 5) for which Fibonacci((p-1)/5) is divisible by p.at n=5A001583
- Denominator of Pi^(2n)/(Gamma(2n)*(1-2^(-2n))*zeta(2n)).at n=5A002425
- a(n) = n^2 written backwards.at n=13A002942
- Tetrahedral numbers written backwards.at n=48A004161
- Divisible only by primes congruent to 1 mod 5.at n=34A004615
- Divisible only by primes congruent to 5 mod 7.at n=33A004623
- Class 4+ primes (for definition see A005105).at n=7A005108
- Class 4- primes (for definition see A005109).at n=12A005112
- Primes p such that 2p-1 is also prime.at n=27A005382
- Primes of the form k^2 + k + 41.at n=25A005846
- Erroneous version of A309982.at n=10A006775
- Record number of steps to reach 1 in '3x+1' problem, corresponding to starting values in A006877.at n=55A006878
- Oscillates under partition transform.at n=33A007212
- Primes whose reversal is a square.at n=3A007488