7181
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 17
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 7392
- Proper Divisor Sum (Aliquot Sum)
- 211
- 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
- 6972
- Möbius Function
- 1
- Radical
- 7181
- 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
- 70
- 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(1)=1, a(n) = smallest odd number such that all sums of pairs of (not necessarily distinct) terms in the sequence are distinct.at n=43A034757
- Numbers whose base-5 representation contains exactly three 1's and three 2's.at n=15A045232
- Partial sums of A000337(n+4), n >= 0.at n=8A045618
- a(1) = 5; a(n) is smallest number >= a(n-1) such that the juxtaposition a(1)a(2)...a(n) is a prime.at n=44A046255
- Discriminants of real quadratic fields with class number 1 and related continued fraction period length of 18.at n=39A050967
- Natural numbers written out with their digits grouped in sets of four (leading zeros omitted).at n=6A091332
- Triangular array formed by the Mersenne numbers.at n=46A110441
- Riordan array (1/(1+3x+2x^2),x/(1+3x+2x^2)).at n=46A111806
- A007318 * A077028.at n=57A134395
- a(n) = ceiling(n*exp(-tan(n))).at n=7A134906
- Numbers k such that k and k^2 use only the digits 1, 5, 6, 7 and 8.at n=6A137060
- Composite numbers generated by the Euler polynomial x^2 + x + 41.at n=9A145292
- G.f.: A(x) = exp( Sum_{n>=1} (1 + 2^n*x)^n * x^n/n ).at n=7A156100
- Number of "ON" cells after n-th stage in simple 2-dimensional cellular automaton (see Comments for precise definition).at n=46A160117
- Wiener index of the n-sun graph.at n=41A180863
- Riordan array T((1-x)^(-2) | 2x-1) read by rows.at n=46A181690
- Number of 8 X n binary arrays without the pattern 0 1 diagonally, vertically, antidiagonally or horizontally.at n=11A188559
- Put the natural numbers together without spaces and read them four at a time advancing one space each time.at n=24A193492
- a(n) = 9*n^2 + 39*n + 83.at n=26A210527
- Rectangular array: (row n) = b**c, where b(h) = -1 + 2^h, c(h) = b(n-1+h), n>=1, h>=1, and ** = convolution.at n=36A213747