7212
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 12
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 12
- Divisor Sum
- 16856
- Proper Divisor Sum (Aliquot Sum)
- 9644
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 2400
- Möbius Function
- 0
- Radical
- 3606
- Omega Function (Ω)
- 4
- 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
- no
- Harshad Number
- yes
- Narcissistic Number
- no
- Collatz Steps
- 44
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
- yes
- Odd
- no
Appears in sequences
- a(0) = 1, a(1) = 0, a(2) = -1; for n >= 3, a(n) = - a(n-2) + Sum_{ primes p with 3 <= p <= n} a(n-p).at n=59A002121
- Egyptian fractions: number of partitions of 1 into reciprocals of positive integers <= n.at n=19A020473
- a(n) = n*(25*n + 1)/2.at n=24A022283
- a(n) = d(n)/2, where d = A026040.at n=32A026041
- Susceptibility series H_4 for 2-dimensional Ising model (divided by 2).at n=7A055856
- Numbers k that, when expressed in base 4 and then interpreted in base 8, give a multiple of k.at n=40A062923
- Harshad numbers which terminate in their digital sum.at n=40A070938
- Interprimes which are of the form s*prime, s=12.at n=21A075287
- a(n) = n*(4*n^2 + 2*n + 1).at n=12A110451
- Multiples of 12 containing a 12 in their decimal representation.at n=40A121032
- Numbers k such that 5^k mod k = 5^k mod k^2.at n=26A125775
- Numbers k such that k^2 divides 5^k-1.at n=21A127105
- Numbers n with property that the sum of the digits of n is substring of n and of n^2.at n=42A162015
- Numbers k such that the sum of the decimal digits of k is a substring of k, of k^2 and of k^3.at n=24A162017
- Number of strings of numbers x(i=1..n) in 0..2 with sum i^3*x(i) equal to n^3*2.at n=19A184250
- Number of 3 X n binary arrays without the pattern 0 1 diagonally, vertically, antidiagonally or horizontally.at n=35A188554
- Number of n-bead necklaces labeled with numbers -1..1 not allowing reversal, with sum zero and first differences in -1..1.at n=15A208986
- Numbers k such that phi(k-6) = phi(k) = phi(k+6).at n=12A217006
- Refactorable numbers between a pair of twin primes.at n=39A226176
- Number of n X 3 0..2 arrays with no element x(i,j) adjacent to value 2-x(i,j) horizontally, vertically or antidiagonally.at n=6A232936