15787
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 28
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 15788
- 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
- 15786
- Möbius Function
- -1
- Radical
- 15787
- 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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 177
- 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
- 1841
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- a(1)=3, b(n) = Product_{k=1..n} a(k), a(n+1) is the smallest prime factor of b(n)-1.at n=32A005265
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 76 ones.at n=21A031844
- Discriminants of imaginary quadratic fields with class number 13 (negated).at n=34A046010
- Irregular primes with irregularity index three.at n=24A060975
- Numbers k such that 10^k - 9^k is prime.at n=9A062576
- Initial term in sequence of four consecutive primes separated by 3 consecutive differences each <=6 (i.e., when d=2,4 or 6) and forming d-pattern=[4, 6,6]; short d-string notation of pattern = [466].at n=22A078852
- Primes p such that the differences between the 5 consecutive primes starting with p are (4,6,6,6).at n=2A078957
- a(1) = 2, a(2) = 3; for n >= 2, a(n+1) is smallest prime factor of (Product_{k = 1..n} a(k)) - 1.at n=32A084598
- Primes p such that p + 2^2, p + 4^2 and p + 6^2 are also primes.at n=24A092475
- Lesser member p of cousin primes (p, p+4) such that (p+1, p+2, p+3) all have the same number of prime divisors (counted with multiplicity).at n=15A094230
- Primes prime(k) such that (prime(k-1) + prime(k+1) + prime(k+2))/prime(k) = 3.at n=29A094933
- Primes p such that 2*p-27, 2*p+27, 2*p-33 and 2*p+33 are primes or -1 times primes.at n=25A103807
- Smallest prime in kx^3+x+2 is prime.at n=22A114366
- Denominators of an Egyptian fraction for e^(-1), using only prime numbers.at n=2A139517
- Primes of the form 210k + 37.at n=35A140847
- Primes congruent to 42 mod 47.at n=34A142393
- Primes congruent to 46 mod 53.at n=33A142576
- Primes congruent to 34 mod 59.at n=30A142761
- Primes congruent to 49 mod 61.at n=25A142847
- T(n,k) = 3*A046802(n,k) - 2*A007318(n,k), triangle read by rows (0 <= k <= n).at n=38A168288