12021
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 6
- Digital Root
- 6
- Palindromic Number
- yes
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 16032
- Proper Divisor Sum (Aliquot Sum)
- 4011
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 8012
- Möbius Function
- 1
- Radical
- 12021
- 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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 143
- 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
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 60 ones.at n=30A031828
- A convolution triangle of numbers, generalizing Pascal's triangle A007318.at n=50A035324
- Numbers n such that determinant[{{n, phi(n), sigma(n)}, {n+1, phi(n+1), sigma(n+1)}, {n+2, phi(n+2), sigma(n+2)}}] is a nonnegative cube.at n=4A067564
- Numbers n of the form k + reverse(k) for exactly three k.at n=26A071914
- Numbers in base -3.at n=22A073785
- a(1) = 1, a(n) = smallest palindrome not included earlier such that a(1)+...+a(n) is a palindrome.at n=28A073880
- a(n) = A078269(n)/11.at n=2A078270
- Palindromic time display in hours, minutes, seconds on a six spaced 24-hour digital clock, using hours 1-24.at n=20A082567
- Palindromes p such that 5p + 1 is also a palindrome.at n=7A083833
- Palindromes n such that 6n + 1 is also a palindrome.at n=7A083835
- Another lazy binary representation of n: similar to A089591 except that the single carry is performed before the increment instead of after.at n=37A089600
- 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=56A100026
- The n-th row of the following array contains all palindromes, with at most n digits, with digit sum n. Sequence contains the array by rows.at n=27A109858
- Triangle, read by rows, equal to the matrix square of triangle A113389. Also given by the matrix product: R^2 = Q^3*(P^-2)*Q, using triangular matrices P=A113370, Q=A113381 and R=A113389.at n=17A113392
- Triangle, read by rows, given by the product R^-1*P^3 using triangular matrices P=A113370, R=A113389.at n=24A114153
- Palindromes equal to the difference between a prime number and its index.at n=42A115889
- Number of even parts in all partitions of n into distinct parts.at n=52A116680
- Palindromic primes in base 6 (written in base 6).at n=14A117701
- Palindromes in base 3 (written in base 3).at n=23A118594
- Palindromes in base 4 (written in base 4).at n=39A118595