12927
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 17920
- Proper Divisor Sum (Aliquot Sum)
- 4993
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 8280
- Möbius Function
- -1
- Radical
- 12927
- Omega Function (Ω)
- 3
- Little Omega Function (ω)
- 3
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
- yes
- Hexagonal Number
- no
- Lucas Number
- no
- Tetrahedral Number
- no
- Pell Number
- no
- Tribonacci Number
- no
- Pronic Number
- no
Recreational
- Happy Number
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 81
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- yes
- 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
Appears in sequences
- Number of plane regions after drawing (in general position) a convex n-gon and all its diagonals.at n=23A027927
- Number of regions in regular n-gon which are quadrilaterals (4-gons) when all its diagonals are drawn.at n=27A067151
- Sum of squares of digits of n is equal to the largest prime factor of n.at n=31A074302
- Number of partitions of n into parts congruent to {0, 1, 3, 5} mod 6.at n=52A096981
- Numbers k such that 7*10^k + 3*R_k - 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=22A103055
- Pentagonal numbers (A000326) which are the sum of 2 other positive pentagonal numbers.at n=19A136117
- a(n) = a(n-1) + Fibonacci(n), a(1)=1983.at n=18A166876
- Numbers k such that Sum_{j=1..k} j^phi(j) == 0 (mod k).at n=13A227429
- a(n) = 3*n*(9*n - 1)/2.at n=31A268351
- Numbers n such that phi(n) = Sum_{j=1..k} d(n^j) for some k, where phi(n) is the Euler totient function of n and d(n) is the number of divisors of n.at n=32A283757
- Pentagonal numbers (A000326) in which parity of digits alternates.at n=19A297644
- Number of faces in the n-polygon diagonal intersection graph.at n=21A301748
- Numbers k such that 347*2^k+1 is prime.at n=22A322971
- Number of integer partitions of n with one fewer distinct multiplicities than distinct parts.at n=42A325244
- Sum of digits when A328316(n) is written in primorial base; number of prime factors in A328316(1+n), counted with multiplicity.at n=10A328319
- a(n) = Sum_{d|n} phi(d) * binomial(d+n/d-1, d).at n=49A338655
- Number of integer partitions of n such that the parts have the same mean as the multiplicities.at n=72A360068
- a(n) = 2*a(n-1) + 1 for a(n-1) not prime, otherwise a(n) = prime(n) - 1; with a(1)=1.at n=32A374965
- Pentagonal numbers which are products of three distinct primes.at n=23A381650