12921
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 15
- Digital Root
- 6
- Palindromic Number
- yes
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 17760
- Proper Divisor Sum (Aliquot Sum)
- 4839
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 8352
- Möbius Function
- -1
- Radical
- 12921
- 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
- no
- 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
- 63
- 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
- Odd palindromes in which parity of digits alternates.at n=39A030148
- Partial sums of usigma(n)^2: square of the sum of unitary divisors of n.at n=26A074789
- Palindromic odd composite numbers that are the products of an odd number of distinct primes.at n=28A075808
- Palindromic odd numbers with exactly 3 prime factors (counted with multiplicity).at n=41A075814
- Last term of n-th row of A077526.at n=11A077525
- Palindromic time display in hours, minutes, seconds on a six spaced 24-hour digital clock, using hours 1-24.at n=29A082567
- a(n) is the odd-length palindrome whose digits up to the center are those of n and whose center digit is equal to the digital root of the product of the factorial of n and the reverse of n.at n=11A082941
- Smallest palindrome > 1 and == 1 (mod n-th palindrome).at n=40A083477
- Short leg of primitive Pythagorean triangles having legs that add up to a square, sorted on hypotenuse.at n=19A089547
- Palindromes n such that 10n01 is a prime.at n=20A099744
- Consider all (2n+1)-digit palindromic primes of the form 10...0M0...01 (so that M is a palindrome with <= 2n-1 digits); a(n) = smallest such M.at n=27A100026
- Concatenation of palindrome k and its 10's complement is prime.at n=33A108537
- Nonnegative values x of solutions (x, y) to the Diophantine equation x^2+(x+79)^2 = y^2.at n=10A118676
- Number of magic labelings of the Petersen graph with magic sum n.at n=11A125196
- Palindromic mountain numbers.at n=15A173070
- Partial sums of Sum_{k=1..n} n/gcd(n,k), or partial sums of Sum_{d|n} d*phi(d) (see A057660).at n=36A174405
- Partial sums of the Floor-Sqrt transform of central binomial coefficients.at n=14A192656
- Happy palindromic numbers.at n=33A216237
- Palindromic nonprime numbers starting with a digit 1.at n=37A222724
- Number of 2 X n 0..2 arrays with antidiagonals unimodal and rows and diagonals nondecreasing.at n=16A224000