13945
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 22
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 16740
- Proper Divisor Sum (Aliquot Sum)
- 2795
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 11152
- Möbius Function
- 1
- Radical
- 13945
- 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
- 151
- 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) = least m such that if r and s in {1/2, 1/4, 1/6, ..., 1/(2*n)} satisfy r < s, then r < k/m < (k+3)/m < s for some integer k.at n=43A024845
- a(n) = (2*n-1)^2 + (2*n)^2.at n=41A060820
- a(n) = (prime(n)^2 + 1)/2.at n=37A066885
- a(n) = 8*n^2 - 4*n + 1.at n=42A080856
- Third row of Pascal-(1,5,1) array A081580.at n=28A081589
- Least k such that prime(n)^2 divides binomial(2k,k).at n=38A110494
- Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0) and consisting of n steps taken from {(-1, -1), (-1, 1), (-1, 0), (0, -1), (0, 1), (1, -1)}.at n=9A151269
- Largest proper divisor of Motzkin number A001006(n).at n=11A153787
- For the n in A157017, the number of representations of n! as the product of distinct numbers in the range n+1 to 2n.at n=75A157229
- Numerators of cumulative sums of rational sequence A038110(k)/A038111(k).at n=6A161527
- G.f.: A(x) = x*exp( Sum_{n>=1} A(A(x)^n)/n ).at n=7A179325
- Numbers k such that k^3 - b2 is a triangular number (A000217), where b2 is the largest square less than k^3.at n=30A233401
- Start with a(1) = 1, a(2) = 3, then a(n)*2^k = a(n+1) + a(n+2), with 2^k the smallest power of 2 (k>0) such that all terms a(n) are positive integers.at n=48A233526
- Numbers k^2 + (k+1)^2 that can be expressed as a sum of two squares in exactly one other way.at n=38A239527
- Smallest number k such that sopf(k)/digsum(k) = prime(n) where sopf(k) is the sum of the distinct primes dividing k and digsum(k) the sum of digits of k.at n=30A241049
- Numbers k such that sigma(2*k-1) is a prime p.at n=12A247820
- a(n) is the numerator of Product_{i=1..n} (1/(1-1/prime(i))) - 1.at n=6A254196
- Array read by antidiagonals: T(n,m) is the number of (undirected) cycles in the rook graph K_n X K_m.at n=17A286418
- Array read by antidiagonals: T(n,m) is the number of (undirected) cycles in the rook graph K_n X K_m.at n=18A286418
- Number of cycles in the 3 X n rook graph.at n=3A341501