16921
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 19
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 16922
- Proper Divisor Sum (Aliquot Sum)
- 1
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 16920
- Möbius Function
- -1
- Radical
- 16921
- Omega Function (Ω)
- 1
- Little Omega Function (ω)
- 1
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
- 84
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 1951
- 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 84 ones.at n=10A031852
- Primes p such that (p+1)/2 and (p+2)/3 are also primes.at n=35A036570
- Primes p such that x^18 = 2 has no solution mod p, but x^6 = 2 has a solution mod p.at n=33A059664
- Primes p such that x^54 = 2 has no solution mod p, but x^6 = 2 has a solution mod p.at n=35A059665
- Primes with 17 as smallest positive primitive root.at n=18A061329
- Initial term in sequence of four consecutive primes whose consecutive differences have d-pattern = [6, 4, 6]; short d-string notation for pattern = [646].at n=23A078856
- Primes p such that the differences between the 5 consecutive primes starting with p are (6,4,6,6).at n=6A078964
- Values of n for which A095777(n) is 16 (those terms which are expressible in decimal digits for bases 2 through 17, but not for base 18).at n=17A095785
- Primes of the form a^4 + b^3 with b>0.at n=34A100271
- Primes of the form x^2 + 1848*y^2.at n=45A139668
- Primes congruent to 14 mod 53.at n=35A142544
- Primes congruent to 47 mod 59.at n=35A142774
- Primes congruent to 24 mod 61.at n=33A142822
- Primes p such that (p+1)/2, (p+2)/3 and (p+3)/4 are also primes.at n=1A163573
- Convolved with its aerated variant of two zeros between terms = A000041.at n=45A174068
- Primes of the form 5^n + n^4.at n=2A182359
- 1/9 the number of (n+1) X 8 0..2 arrays with all 2 X 2 subblocks having the same four values.at n=12A184046
- Primes of the form 2n^2 - 7.at n=26A201714
- Primes of the form 8n^2 - 7.at n=10A201858
- Numbers of the form 5^j + 6^k, for j and k >= 0.at n=40A226814