12131
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 8
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 13872
- Proper Divisor Sum (Aliquot Sum)
- 1741
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 10392
- Möbius Function
- 1
- Radical
- 12131
- Omega Function (Ω)
- 2
- 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
- no
- Narcissistic Number
- no
- Collatz Steps
- 24
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- yes
- 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
- a(n) = Sum_{k=1..floor((n+1)/2)} T(n,2k-1), array T as in A049777.at n=40A049778
- House numbers: a(n) = (n+1)^3 + Sum_{i=1..n} i^2.at n=20A051662
- Interprimes which are of the form s*prime, s=7.at n=16A075282
- Numbers k such that average of prime(k) and prime(k+1) is a perfect square.at n=46A076692
- Partition the concatenation 1234567...of natural numbers into successive strings which are multiples of 7, all different and > 7 (0 is never taken as the most significant digit).at n=1A077300
- a(1) = 1; then the smallest number such that both the forward and reverse n-th partial concatenation is a prime for n > 1. (Reverse concatenation is taken term-wise and not digit-wise.)at n=22A083992
- Triangle read by rows: T(n,k) is the number of strongly connected directed multigraphs with loops, with n arcs and k vertices.at n=51A139622
- Numbers k such that k^p+p is prime, where p is product of the digits of k.at n=3A178327
- Starting with 1, smallest integer not yet in the sequence such that two neighboring digits of the sequence multiply to a prime.at n=36A182271
- Number of nX3 0..2 arrays with every element equal to either the sum mod 3 of its vertical neighbors or the sum mod 3 of its horizontal neighbors.at n=5A183477
- Number of nX6 0..2 arrays with every element equal to either the sum mod 3 of its vertical neighbors or the sum mod 3 of its horizontal neighbors.at n=2A183480
- T(n,k)=Number of nXk 0..2 arrays with every element equal to either the sum mod 3 of its vertical neighbors or the sum mod 3 of its horizontal neighbors.at n=30A183483
- T(n,k)=Number of nXk 0..2 arrays with every element equal to either the sum mod 3 of its vertical neighbors or the sum mod 3 of its horizontal neighbors.at n=33A183483
- Put the natural numbers together without spaces and read them five at a time advancing one space each time.at n=13A193493
- Odd numbers producing 5 odd numbers in the Collatz iteration.at n=40A198588
- Odd numbers producing 20 even numbers in the Collatz iteration.at n=35A199818
- Numbers whose product of digits is 6.at n=40A199988
- Composite numbers whose product of digits is 6.at n=26A201055
- Euler transform of period 5 sequence [ 2, 1, 1, 2, 1, ...].at n=23A205183
- Sum_{0<j<n} (n^4-j^4).at n=5A206810