7815
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 12528
- Proper Divisor Sum (Aliquot Sum)
- 4713
- 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
- 4160
- Möbius Function
- -1
- Radical
- 7815
- Omega Function (Ω)
- 3
- Little Omega Function (ω)
- 3
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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 132
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- 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
- a(n) = floor(n*phi^13), where phi is the golden ratio, A001622.at n=15A004928
- a(n) = round(n*phi^13), where phi is the golden ratio, A001622.at n=15A004948
- Number of weighted voting procedures.at n=13A005257
- Smallest positive number that can be written as sum of distinct Fibonacci numbers in n ways.at n=78A013583
- a(0)=0, a(1)=1, a(2)=2; for n > 2, a(n) = 3*a(n-1) - a(n-2) - 2*a(n-3).at n=13A027934
- Number of partitions of n into parts not of the form 23k, 23k+4 or 23k-4. Also number of partitions with at most 3 parts of size 1 and differences between parts at distance 10 are greater than 1.at n=34A035992
- a(n) = A045820(n)/2.at n=12A045822
- a(n) = T(n,n-5), array T as in A055807.at n=15A055810
- Numbers k such that k^18 == 1 (mod 19^3).at n=21A056089
- Largest number of straight line crossing-free spanning trees on n points in the plane.at n=4A063548
- The terms of A055237 (sums of two powers of 5) divided by 2.at n=22A073217
- Triangle read by rows: T(n,k) is the number of compositions of n into k parts when parts equal to q are of q^2 kinds.at n=40A105495
- Triangle read by rows: T(n,k) = n*(1+n^k)/2, 0<=k<=n.at n=20A108396
- a(n) = n*(1 + n^n)/2.at n=5A108398
- Diagonal sums of the Riordan array A116382.at n=14A116384
- Multiples of 15 containing a 15 in their decimal representation.at n=38A121035
- Total Wiener index of (rooted?) trees on n nodes (see Wagner for precise definition).at n=7A122682
- Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (-1, 0, 1), (1, 0, 0), (1, 0, 1), (1, 1, -1)}.at n=7A150506
- Number of peaks at odd level in all Dyck paths of semilength n with no UUU's and no DDD's, (U=(1,1), D=(1,-1)). These Dyck paths are counted by the secondary structure numbers (A004148).at n=11A166292
- a(n) = n*(n^5 + 1)/2.at n=5A167963