531
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 9
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 780
- Proper Divisor Sum (Aliquot Sum)
- 249
- 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
- 348
- Möbius Function
- 0
- Radical
- 177
- Omega Function (Ω)
- 3
- Little Omega Function (ω)
- 2
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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 123
- Smith Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- Prime Power
- no
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Names
- German
- fünfhunderteinunddreißig· ordinal: fünfhunderteinunddreißigste
- English
- five hundred thirty-one· ordinal: five hundred thirty-first
- Spanish
- quinientos treinta y uno· ordinal: 531º
- French
- cinq cent trente et un· ordinal: cinq cent trente et unième
- Italian
- cinquecentotrentuno· ordinal: 531º
- Latin
- quingenti triginta unus· ordinal: 531.
- Portuguese
- quinhentos e trinta e um· ordinal: 531º
Appears in sequences
- Number of positive integers <= 2^n of form x^2 + 3 y^2.at n=11A000205
- Moran numbers: k such that k/(sum of digits of k) is prime.at n=40A001101
- Generalized divisor function. Number of partitions of n with exactly three part sizes.at n=18A002134
- Take solution to Pellian equation x^2 - n*y^2 = 1 with smallest positive y and x >= 0; sequence gives a(n) = y, or 0 if n is a square. A002350 gives values of x.at n=42A002349
- Number of n-node trees with a forbidden limb of length 6.at n=12A002992
- Numbers that are the sum of 6 positive 4th powers.at n=39A003340
- Numbers that are the sum of 10 positive 5th powers.at n=22A003355
- Inconsummate numbers in base 10: no number is this multiple of the sum of its digits (in base 10).at n=50A003635
- Reverse digits of number of partitions of n.at n=14A004089
- Divisible only by primes congruent to 3 mod 7.at n=34A004621
- Primes written in base 6.at n=45A004680
- Number of Twopins positions.at n=33A005686
- Positions of remoteness 5 in Beans-Don't-Talk.at n=22A005697
- a(n) = a(n-1) + a(n-9) for n >= 9; a(n) = 1 for n=0..7; a(8) = 2.at n=36A005711
- Number of fractions in Farey series of order n.at n=41A005728
- Sums of prime divisors of Ruth-Aaron numbers (A006145).at n=55A006146
- Number of factorization patterns of polynomials of degree n over F_5.at n=11A006170
- Number of n-node animals on f.c.c. lattice (invert A007199).at n=4A006194
- a(n) = a(n-1) + a(n - 1 - number of even terms so far).at n=21A006336
- Solution to Pellian: y such that x^2 - n*y^2 = +-1.at n=42A006703