15991
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
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 15992
- 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
- 15990
- Möbius Function
- -1
- Radical
- 15991
- 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
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 1862
- 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 76 ones.at n=22A031844
- Primes with 12 as smallest positive primitive root.at n=4A061325
- Position of first repeat of the opening sequence of length n occurring after the first repeat of the opening sequence of length n-1 in the Kolakoski sequence (A000002).at n=33A074300
- Records in A079387.at n=13A079388
- Beginning with 3, least prime, greater than the previous term, such that the arithmetic mean of first n terms is a prime.at n=37A090918
- Primes of the form 55x^2+10xy+199y^2.at n=28A140632
- Primes of the form 210k + 31.at n=35A140846
- Primes congruent to 11 mod 47.at n=38A142362
- Primes congruent to 38 mod 53.at n=36A142568
- Primes congruent to 2 mod 59.at n=33A142729
- Primes congruent to 9 mod 61.at n=32A142807
- Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (-1, -1, 1), (-1, 0, 1), (0, 1, -1), (1, 0, 1)}.at n=9A148922
- Prime p1 of consecutive primes p1, p2, where p2-p1=10, and p1, p2 are in different centuries.at n=17A160500
- Primes p such that p^3-p^2-1 and p^3-p^2+1 are prime.at n=24A160858
- a(n) is the smallest term m in A173978 for which A020639(2m-3) = prime(n), n > 1.at n=28A173980
- Primes p such that 10p+1 divides 2^p-1.at n=35A188133
- Primes of the form 3n^2 + 4.at n=15A201477
- Primes of the form 10n^2 - 9.at n=15A201964
- Primes p whose smallest positive primitive root (mod p) is not squarefree.at n=4A205581
- Smallest of five consecutive primes whose sum is a square.at n=9A206281