15919
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
- 15920
- 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
- 15918
- Möbius Function
- -1
- Radical
- 15919
- 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
- 221
- 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
- 1856
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Discriminants of quintic fields with 2 complex conjugates (negated).at n=25A023684
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 98 ones.at n=11A031866
- Last member of a sexy prime quadruple: value of p+18 such that p, p+6, p+12 and p+18 are all prime.at n=31A046124
- a(n) = Sum_{i=0..n} T(i,n-i), array T as in A049723.at n=24A049724
- Fourth term of balanced prime quartets: p(m-2)-p(m-3) = p(m-1)-p(m-2) = p(m)-p(m-1).at n=11A054803
- a(n) is the smallest emirp that is the first of n consecutive emirps with equal digit sum.at n=2A071614
- Right diagonal of triangle in A072467.at n=20A072469
- a(n) = smallest prime p_k such that the n successive differences between the primes p_k through p_(k+n) are all distinct.at n=10A079007
- Primes indexed by A078515; i.e., primes which start record runs of consecutive primes with distinct first differences.at n=8A079889
- Number of primitive Pythagorean triples with hypotenuse < 10^n.at n=4A101931
- Number of products of factorials not exceeding n!.at n=22A101976
- Sequence of primes based on the powers of the golden mean; see formula section for description.at n=13A114345
- Primes congruent to 9 mod 43.at n=38A142258
- Primes congruent to 19 mod 53.at n=40A142549
- Primes congruent to 48 mod 59.at n=36A142775
- Primes congruent to 59 mod 61.at n=32A142857
- Emirps whose only prime digits are 5's.at n=25A179036
- Emirps with a 5 as the only prime digit.at n=19A179037
- Number of 2X4 integer matrices with each row summing to zero, row elements in nondecreasing order, rows in lexicographically nondecreasing order, and the sum of squares of the elements <= 2*n^2 (number of collections of 2 zero-sum 4-vectors with total modulus squared not more than 2*n^2, ignoring vector and component permutations).at n=9A192699
- Let p_(4,3)(m) be the m-th prime == 3 (mod 4). Then a(n) is the smallest p_(4,3)(m) such that the interval(p_(4,3)(m)*n, p_(4,3)(m+1)*n) contains exactly one prime == 3(mod 4).at n=33A210476