7819
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 25
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 8944
- Proper Divisor Sum (Aliquot Sum)
- 1125
- 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
- 6696
- Möbius Function
- 1
- Radical
- 7819
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 2
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
- 39
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- yes
- Squarefree Number
- yes
- Prime Power
- no
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Numbers k such that the continued fraction for sqrt(k) has period 74.at n=19A020413
- Sums of distinct powers of 6.at n=39A033043
- First differences give (essentially) A028242.at n=41A035107
- Number of partitions of n into parts not of form 4k+2, 16k, 16k+5 or 16k-5.at n=51A036022
- Composite numbers whose prime factors contain no digits other than 1 and 7.at n=26A036307
- Positive numbers having the same set of digits in base 2 and base 6.at n=35A037411
- Sums of 4 distinct powers of 6.at n=5A038480
- Numbers having four 1's in base 6.at n=25A043376
- Semiprimes whose prime factors, when concatenated, yield a palindrome.at n=44A046451
- a(n) = a(n-1) + a(n - 1 minus the number of terms of a(k) == n (mod 3) so far).at n=35A060730
- a(n) is the smallest positive integer such that no term in S={a(1),...,a(n)}, n>=3, divides the sum of any two other distinct terms of S, after first initializing the sequence with a(1)=3 and a(2)=4.at n=36A068573
- Square array A(n>=0,k>=1) (listed antidiagonally: A(0,1)=1, A(1,1)=1, A(0,2)=1, A(2,1)=2, A(1,2)=1, A(0,3)=1, A(3,1)=3, ...) giving the number of n-edge general plane trees fixed by k-fold application of Catalan Automorphisms A057511/A057512 (Deep rotation of general parenthesizations/plane trees).at n=79A079216
- Triangle T(n,d) (listed row-wise: T(1,1)=1, T(2,1)=1, T(2,2)=1, T(3,1)=2, T(3,2)=2, T(3,3)=1, ...) giving the number of n-edge general plane trees with root degree d that are fixed by the two-fold application of Catalan Automorphisms A057511/A057512 (Deep rotation of general parenthesizations/plane trees).at n=66A079218
- Number of Catalan objects fixed by two-fold application of the Catalan bijections A057511/A057512 (Deep rotation of general parenthesizations/plane trees).at n=11A079223
- a(1) = 4 and then least composite such that every partial concatenation of 2 or more terms is a prime.at n=44A086474
- a(n+1) = 4*a(n) + 11*a(n-1) - 2*a(n-3).at n=5A122884
- Interlaced merger of A122883, A122884 and A122885.at n=19A122886
- Triangle T(n,k) read by rows: number of permutations in [n] with exactly k ascents that have an even number of inversions.at n=31A128612
- Triangle T(n,k) read by rows: number of permutations in [n] with exactly k ascents that have an even number of inversions.at n=32A128612
- Numerators of coefficients in series expansion of 1/(Bernoulli trial entropy).at n=61A145176