15971
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 23
- Digital Root
- 5
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 15972
- 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
- 15970
- Möbius Function
- -1
- Radical
- 15971
- 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
- 53
- 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
- 1860
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Numbers k such that the continued fraction for sqrt(k) has period 98.at n=33A020437
- Smallest nonempty set S containing prime divisors of 10k+1 for each k in S.at n=39A020632
- a(n) = T(2n-1,n-1), T given by A026648.at n=7A026652
- a(n) = T(n,[ n/2 ]), T given by A026648.at n=15A026654
- Recursive prime generating sequence.at n=52A039726
- Let (p1,p2), (p3,p4) be pairs of twin primes with p1*p2=p3+p4-1; sequence gives values of p1.at n=19A047976
- a(1) = 1, a(n) = a(n - 1) + pi(a(n - 1)) + 1.at n=44A065962
- Numbers k such that sigma(k+2) - sigma(k) = prime(k+1) - prime(k).at n=36A067062
- Primes p such that 11 is the largest of all prime factors of the numbers between p and the next prime (cf. A052248).at n=18A080187
- Lessers of twin prime pairs whose greater has a prime prime index.at n=42A094068
- Primes A005382(n) + A005384(n) - 1 with a twin prime A005382(n) + A005384(n) + 1.at n=23A099109
- Primes of the form A108656(n-2)*n^2+A108656(n-1)*n+A108656(n).at n=41A108657
- Lesser of twin primes isolated from neighboring primes by +- 10 (or more).at n=29A138063
- Primes of the form 210n+11.at n=37A140840
- Primes congruent to 18 mod 53.at n=37A142548
- Primes congruent to 41 mod 59.at n=25A142768
- Primes congruent to 50 mod 61.at n=30A142848
- a(n) = 484*n - 1.at n=32A158330
- Largest prime factor of number formed from a(n-1) with a 1 added at the end, a(1)=2.at n=21A165978
- Largest prime factor of number formed from a(n-1) with a 1 added at the end, a(1)=2.at n=28A165978