7215
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 15
- Digital Root
- 6
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 16
- Divisor Sum
- 12768
- Proper Divisor Sum (Aliquot Sum)
- 5553
- 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
- 3456
- Möbius Function
- 1
- Radical
- 7215
- Omega Function (Ω)
- 4
- Little Omega Function (ω)
- 4
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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 70
- 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) = 2*a(n-1) + a(n-2) - a(n-3), with a(0) = a(1) = 0, a(2) = 1.at n=13A006054
- Coordination sequence for FeS2-Pyrite, S position.at n=41A009956
- Orders of cyclotomic polynomials containing a coefficient the absolute value of which is >= 5.at n=33A013593
- Lucky numbers with size of gaps equal to 16 (lower terms).at n=21A031898
- a(n) = prime(n)*prime(n+1) - prime(n) - prime(n+1).at n=22A037165
- 3-wave sequence starting with 1, 1, 1.at n=23A038196
- Number of partitions satisfying cn(1,5) + cn(4,5) <= cn(2,5) and cn(1,5) + cn(4,5) <= cn(3,5).at n=42A039876
- Sum of consecutive nonsquares.at n=15A048395
- a(n) = 5*n^2 + 10*n.at n=36A067724
- Harshad numbers which terminate in their digital sum.at n=41A070938
- 2-apexes of omega: numbers k such that omega(k-2) < omega(k-1) < omega(k) > omega(k+1) > omega(k+2), where omega(m) = the number of distinct prime factors of m.at n=39A076762
- Numbers k such that (k / sum of digits of k) and (k+1 / sum of digits of k+1) are both semiprime.at n=14A085774
- Consider recurrence b(0) = (2n+1)/2, b(n) = b(0)*floor(b(n-1)); sequence gives first integer reached.at n=17A087675
- Odd squarefree numbers k such that k/phi(k) > 2, where phi is Euler's totient function.at n=41A091495
- Numbers m that are the hypotenuse of exactly 13 distinct integer-sided right triangles, i.e., m^2 can be written as a sum of two squares in 13 ways.at n=32A097102
- Expansion of g.f.: 1/(1 - 2*x - x^2 + x^3).at n=11A106805
- Numbers n such that p(3n) is prime, where p(n) is the number of partitions of n.at n=38A111389
- Numbers k such that F(2*k + 1) is prime where F(m) is a Fibonacci number.at n=25A117517
- Expansion of ( 1-x^3+x^4+x^5-x^8 ) / ( 1-2*x^3-x^6+x^9 ).at n=37A120771
- Multiples of 15 containing a 15 in their decimal representation.at n=36A121035