10921
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 11152
- Proper Divisor Sum (Aliquot Sum)
- 231
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 10692
- Möbius Function
- 1
- Radical
- 10921
- 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
- 161
- 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
- (n-th Fibonacci number that is not 1) - (n-th number that is 1 or not a Fibonacci number).at n=18A014242
- Smallest k such that the smallest palindrome > k in the Reverse and Add! trajectory of k is reached after exactly n iterations.at n=26A015994
- a(0) = 0. For n > 0, smallest non-palindromic number k such that the smallest palindrome in the Reverse and Add! trajectory of k is reached after exactly n iterations.at n=27A023109
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 82 ones.at n=3A031850
- Least number of Reverse-then-add persistence n.at n=27A033866
- Decimal part of n-th root of a(n) starts with digit 2.at n=49A034079
- Numbers k such that the k-th Fibonacci number reversed is prime.at n=26A036971
- Number of triples {i,j,k}, i>1, j>1, k>1, such that i*j*k < n^3.at n=13A037092
- Numbers whose base-2 representation has exactly 13 runs.at n=6A043580
- a(n) = floor(e^n / n^e).at n=16A062277
- Centered 14-gonal numbers.at n=39A069127
- a(n) = 16*n^2 + 4*n + 1.at n=26A082041
- a(n) = (8*2^n-5*(-1)^n)/3.at n=12A083582
- a(n) = (8*4^n - 5)/3.at n=6A083584
- Expansion of x*(1+2*x)/((1+x)*(1-x)*(1-2*x)).at n=13A084639
- a(n) = Sum_{d|n} (n-1)!/(d-1)!.at n=7A087906
- Expansion of (1-x+2*x^2)/((1-x)*(1-x-2*x^2)).at n=13A097074
- Expansion of x^3 / ((x-1)*(2*x-1)*(x^2-x+1)).at n=15A111927
- Odd numbers n for which 17 is the smallest i (>= 1) with Jacobi symbol J(i,n) getting either a value 0 or -1.at n=11A112077
- Semiprimes in A056109.at n=27A113528