3781
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 19
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 4
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 4000
- Proper Divisor Sum (Aliquot Sum)
- 219
- 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
- 3564
- Möbius Function
- 1
- Radical
- 3781
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 38
- 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
- Hex (or centered hexagonal) numbers: 3*n*(n+1)+1 (crystal ball sequence for hexagonal lattice).at n=35A003215
- a(n) = floor(n*phi^11), where phi is the golden ratio, A001622.at n=19A004926
- a(n) = round(n*phi^11), where phi is the golden ratio, A001622.at n=19A004946
- Independence number of de Bruijn graph of order n on two symbols.at n=12A006946
- Coordination sequence T2 for Zeolite Code LTL.at n=45A008139
- Coordination sequence T2 for Zeolite Code MTN.at n=37A008187
- Generalized Fibonacci numbers: a(n) = a(n-1) + 9*a(n-2).at n=7A015445
- Pseudoprimes to base 21.at n=14A020149
- Pseudoprimes to base 24.at n=21A020152
- Pseudoprimes to base 37.at n=47A020165
- Pseudoprimes to base 43.at n=41A020171
- Pseudoprimes to base 58.at n=23A020186
- Pseudoprimes to base 92.at n=34A020220
- Pseudoprimes to base 93.at n=28A020221
- Strong pseudoprimes to base 21.at n=3A020247
- Strong pseudoprimes to base 37.at n=7A020263
- Strong pseudoprimes to base 43.at n=8A020269
- Strong pseudoprimes to base 58.at n=7A020284
- Strong pseudoprimes to base 92.at n=11A020318
- a(n) = n*(21*n-1)/2.at n=19A022278