12981
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 17312
- Proper Divisor Sum (Aliquot Sum)
- 4331
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 8652
- Möbius Function
- 1
- Radical
- 12981
- 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
- 138
- 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
- a(n) = [ a(n-1)/a(1) + a(n-3)/a(3) + a(n-5)/a(5) + ... ], for n >= 3.at n=30A022865
- Number of partitions satisfying cn(0,5) + cn(1,5) + cn(4,5) <= cn(2,5) + cn(3,5).at n=39A039878
- Number of distinct partitions of n-th triangular number which can be obtained by merging parts in the partition 1+2+...+n.at n=10A066723
- Indices of the start of a string of 24 consecutive squares whose sum is a square.at n=18A094196
- Number of (n+1)X(1+1) 0..3 arrays with the maximum plus the lower median minus the minimum of every 2X2 subblock differing from its horizontal and vertical neighbors by exactly one.at n=2A238140
- Number of (n+1)X(3+1) 0..3 arrays with the maximum plus the lower median minus the minimum of every 2X2 subblock differing from its horizontal and vertical neighbors by exactly one.at n=0A238142
- T(n,k)=Number of (n+1)X(k+1) 0..3 arrays with the maximum plus the lower median minus the minimum of every 2X2 subblock differing from its horizontal and vertical neighbors by exactly one.at n=3A238145
- T(n,k)=Number of (n+1)X(k+1) 0..3 arrays with the maximum plus the lower median minus the minimum of every 2X2 subblock differing from its horizontal and vertical neighbors by exactly one.at n=5A238145
- a(n) = r*a(ceiling(n/2))+s*a(floor(n/2)) with a(1)=1 and (r,s)=(4,1).at n=44A268527
- a(n) = a(n-1) + 3*a(n-2) -2*a(n-3) - 2*a(n-4), where a(0) = -2, a(1) = 0, a(2) = 0, a(3) = 1.at n=18A295858