2819
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 2820
- 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
- 2818
- Möbius Function
- -1
- Radical
- 2819
- 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
- 84
- 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
- yes
- Safe Prime
- yes
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 410
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Primes p == 7, 19, 23 (mod 40) such that (p-1)/2 is also prime.at n=23A000353
- The game of Mousetrap with n cards: the number of permutations of n cards having at least one hit after 2.at n=7A002468
- Lucasian primes: p == 3 (mod 4) with 2*p+1 prime.at n=40A002515
- A generalized partition function.at n=14A002599
- Safe primes p: (p-1)/2 is also prime.at n=45A005385
- Prime self (or Colombian) numbers: primes not expressible as the sum of an integer and its digit sum.at n=43A006378
- Numbers n such that n, 2n+1, and 4n+3 all prime.at n=22A007700
- Coordination sequence T2 for Zeolite Code AEL.at n=35A008005
- Coordination sequence T3 for Zeolite Code EUO.at n=33A008098
- Coordination sequence T1 for Zeolite Code WEI.at n=38A009917
- Coordination sequence for Ni2In, Position Ni1 and In.at n=16A009941
- Odd primes such that (3p+1)/2 and 3p+4 are also prime.at n=28A014223
- From George Gilbert's marks problem: jumping 6 marks at a time (final positions).at n=8A019996
- Numbers k such that the continued fraction for sqrt(k) has period 42.at n=24A020381
- a(n) = [ a(n-1)/a(1) ] + [ a(n-2)/a(2) ] + ... + [ a(1)/a(n-1) ], for n >= 3.at n=15A022858
- Primes that remain prime through 2 iterations of function f(x) = 4x + 3.at n=38A023250
- Primes that remain prime through 2 iterations of function f(x) = 6x + 7.at n=38A023258
- Primes that remain prime through 2 iterations of function f(x) = 7x + 6.at n=35A023259
- Primes that remain prime through 2 iterations of function f(x) = 9x + 2.at n=41A023265
- Primes that remain prime through 3 iterations of function f(x) = 3x + 10.at n=19A023280