1831
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 1832
- Proper Divisor Sum (Aliquot Sum)
- 1
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 1830
- Möbius Function
- -1
- Radical
- 1831
- 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
- 68
- 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
- 282
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- a(0)=2; for n>=1, a(n) = smallest prime p such that there is a gap of exactly 2n between p and next prime, or -1 if no such prime exists.at n=8A000230
- Primes p of the form 3k+1 such that -sqrt(p) < sum_{x=1..p} cos(2*Pi*x^3/p) < sqrt(p).at n=41A000922
- Primes p such that the multiplicative order of 2 modulo p is (p-1)/6.at n=11A001136
- Indices of primes where largest gap occurs.at n=11A005669
- a(n) = C(n+2,3) + C(n,3) + C(n-1,3).at n=15A006004
- Reflectable emirps.at n=11A007628
- Year of birth of n-th President of U.S.A.at n=19A008745
- Primes of the form x^2 + 27y^2.at n=43A014752
- Primes that are palindromic in base 2 (but written here in base 10).at n=16A016041
- Numbers k=3*m+1 such that 2^m == 1 (mod k).at n=45A016108
- Numbers k such that the continued fraction for sqrt(k) has period 84.at n=0A020423
- Index of 5^n within sequence of numbers of form 2^i * 5^j.at n=39A022334
- Primes that remain prime through 2 iterations of the function f(x) = 2x + 9.at n=39A023245
- Primes that remain prime through 2 iterations of function f(x) = 3x + 10.at n=47A023249
- Primes that remain prime through 2 iterations of function f(x) = 7x + 6.at n=23A023259
- Primes that remain prime through 2 iterations of function f(x) = 9x + 2.at n=30A023265
- Number of partitions of n into an even number of parts, the least being 2; also, a(n+2) = number of partitions of n into an odd number of parts, each >=2.at n=38A027194
- Palindromic primes in base 16 (or hexadecimal), but written here in base 10.at n=20A029732
- Inverse Euler transform of {1, primes}.at n=45A030011
- Primes which when concatenated with next 3 primes are also prime.at n=22A030472