15661
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 19
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 15662
- 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
- 15660
- Möbius Function
- -1
- Radical
- 15661
- 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
- 102
- 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
- 1827
- 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) = 10x + 9.at n=38A023301
- Numerators of continued fraction convergents to sqrt(392).at n=6A041744
- Numbers whose base-5 representation contains exactly three 0's and three 1's.at n=13A045172
- First occurrence prime gaps of the primes in sequence A002313 (Real primes with corresponding complex primes). a(0) = 2 with length of gap 3. For n>0 the size of the gap in the sequence is 4n, a(n) is the starting prime of the gap.at n=18A084160
- Primes that are the sum of two squares and which set a record for the gap to the next prime of that form.at n=10A084161
- Prime Friedman numbers.at n=8A112419
- Combining the conditional divide-by-two concept from Collatz sequences with Pascal's triangle, we can arrive at a new kind of triangle. Start with an initial row of just 4. To compute subsequent rows, start by appending a zero to the beginning and end of the previous row. Like Pascal's triangle, add adjacent terms of the previous row to create each of the subsequent terms. The only change is that each term is divided by two if it is even. Then take the center of this triangle. In other words, take the n-th term from the (2n)th row.at n=18A123403
- Primes in A132286.at n=37A132287
- Primes congruent to 9 mod 43.at n=37A142258
- Primes congruent to 26 mod 53.at n=33A142556
- Primes congruent to 26 mod 59.at n=26A142753
- Primes congruent to 45 mod 61.at n=31A142843
- Primes p such that (p-1)*p*(p+1)-p+2 and (p-1)*p*(p+1)+p-2 are primes.at n=25A154944
- Primes that can be written as a sum of a positive square and a positive cube in more than one way.at n=32A162930
- Primes p such that (p reversed)-10 is a square.at n=22A167475
- Expansion of x/(1 - 4*x + 3*x^2 - 2*x^3).at n=9A175005
- Primes of the form 2*n^2+6*n+1.at n=14A176549
- The smaller member prime(i) of an emirp pair (prime(i),prime(j)), such that the digit sum of i equals the digit sum of j.at n=15A178613
- Emirps whose only prime digits are 5's.at n=24A179036
- Emirps with a 5 as the only prime digit.at n=18A179037