17921
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 17922
- 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
- 17920
- Möbius Function
- -1
- Radical
- 17921
- 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
- 92
- 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
- yes
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 2054
- 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 66 ones.at n=34A031834
- Values of A (the short leg) of a Pythagorean triangle with A and C (the hypotenuse) both prime and part of a twin prime.at n=31A051642
- a(n) = 512*n + 1.at n=35A076338
- Primes of the form 512*k+1.at n=6A076339
- Smallest prime of the form 1 followed by a perfect power.at n=20A089773
- Number of partitions of n in which no parts are multiples of 25.at n=36A092885
- Primes prime(k) such that (prime(k-1) + prime(k+1) + prime(k+2))/prime(k) = 3.at n=32A094933
- Primes of the form 1024n + 513.at n=3A105132
- Primes of the form 2^a * 5^b * 7^c + 1 for positive a, b, c.at n=10A114992
- First Hadamard-Sylvester matrix self -similar matrix based on the Padovan/ Minimal Pisot 3 X 3 matrix as an 9 X 9 matrix: Characteristic Polynomial:1 - x - x^3 - x^4 - x^5 + 3 x^6 + 2 x^7 - x^9.at n=15A121230
- Prime numbers p of the form 10k+1 for which the quintic polynomial x^5-x-1 modulus p is factorizable into five binomials.at n=3A135842
- Prime numbers p for which the quintic polynomial x^5 - x - 1 modulo p completely factors into linear polynomials.at n=10A135844
- Primes congruent to 7 mod 53.at n=39A142537
- Primes congruent to 44 mod 59.at n=35A142771
- Primes congruent to 48 mod 61.at n=32A142846
- Primes congruent to 32 mod 67.at n=34A154621
- a(n) = 70*n^2 + 1.at n=16A158734
- Primes of the form k * m^m + 1 with k < m^m.at n=22A180362
- Primes of the form x^3 + y^3 + 1.at n=43A188620
- Number of nondecreasing arrangements of n+2 numbers in 0..n with the last equal to n and each after the second equal to the sum of one or two of the preceding three.at n=17A190034