16981
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 25
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 16982
- 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
- 16980
- Möbius Function
- -1
- Radical
- 16981
- 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
- 128
- 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
- 1958
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Primes that remain prime through 3 iterations of function f(x) = 5x + 8.at n=27A023286
- Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 28.at n=3A031616
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 66 ones.at n=28A031834
- "AFJ" (ordered, size, labeled) transform of 1,3,5,7,...at n=7A032003
- P(p(n)), P = primes (A000040), p = partition numbers (A000041).at n=25A058697
- Primes p such that the sum of the digits of p is not prime, but the sum of the cubes of the digits of p is prime.at n=25A091365
- Column 6 of array illustrated in A089574 and related to A034261.at n=6A107601
- Primes of the form 256 k + 85.at n=15A127593
- Primes congruent to 21 mod 53.at n=40A142551
- Primes congruent to 48 mod 59.at n=38A142775
- Primes congruent to 23 mod 61.at n=33A142821
- Primes which become emirps when rotated by 180 degrees on a digital clock display.at n=14A145750
- Lesser of two consecutive primes, p < q, such that both p*q+p-q and p*q-p+q are prime numbers.at n=24A154553
- Primes dividing some member of A073833.at n=37A161500
- Primes p such that q*p+-Mod(p,q) are primes, for q=7.at n=24A178387
- First of a run of 4 or more consecutive primes which all equal 1 (mod 3).at n=33A185942
- Lesser of two consecutive primes, p < q, such that p*q + p - q and p*q - p + q are also consecutive primes.at n=13A225726
- Primes p such that p-2 and q are primes, where q is concatenation of binary representations of p and p-2: q = p * 2^L + p-2, where L is the length of binary representation of p-2: L=A070939(p-2).at n=18A232237
- Primes of the form n^2 + 81.at n=15A256775
- Primes p such that A001175(p) = (p-1)/6.at n=17A308791