15287
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
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 15288
- 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
- 15286
- Möbius Function
- -1
- Radical
- 15287
- 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
- 71
- 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
- yes
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 1785
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Smallest number of complexity n: smallest number requiring n 1's to build using + and *.at n=32A005520
- Smaller term of closest safe prime pairs.at n=15A059323
- Irregular primes with irregularity index three.at n=23A060975
- Primes p such that (p-1)/2 and (p-3)/4 are also prime.at n=26A066179
- Number of ways of arranging the numbers 1..n in a circle so that there is no consecutive triple i, i+1, i+2 or i, i-1, i-2 (mod n).at n=8A078673
- Least k such that the class number of quadratic order of discriminant D=-4k equals p, where p runs through the primes.at n=32A079029
- Primes p such that 13 is the largest of all prime factors of the numbers between p and the next prime (cf. A052248).at n=19A080188
- Numbers which are primes and which remain prime for three successive applications of incrementing each digit by 2 with carries ignored.at n=19A088787
- Primes p such that little googol - p is prime.at n=33A108256
- Primes congruent to 22 mod 43.at n=39A142271
- Primes congruent to 23 mod 53.at n=32A142553
- Primes congruent to 6 mod 59.at n=29A142733
- Primes congruent to 37 mod 61.at n=29A142835
- a(n) = 78*n^2 - 1.at n=13A158771
- Primes p of the form 6n-1 such that p-1 is a semiprime and p+2 is prime or prime squared.at n=43A181669
- Primes p of the form p = prime(n) + prime(n+1) - 5 and p = prime(k) + prime(k+1) + 5.at n=30A207992
- Number of (n+2) X (3+2) 0..3 arrays with every consecutive three elements in every row and column having exactly two distinct values, and in every diagonal and antidiagonal not having exactly two distinct values, and new values 0 upwards introduced in row major order.at n=11A252690
- Subtract 1 from the terms of A256407.at n=26A256410
- a(0) = 2; for n>0, a(n) = smallest prime p such that p > a(n-1) and p is congruent to n modulo prime(n).at n=36A261192
- a(n) = gpf(1 + Product_{k=0..4} prime(n+k)), where gpf is greatest prime factor and prime(i) is the i-th prime.at n=22A261210