3981
domain: N
Properties
Digital Properties
- Digit Count
- 4
- 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
- 5312
- Proper Divisor Sum (Aliquot Sum)
- 1331
- 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
- 2652
- Möbius Function
- 1
- Radical
- 3981
- 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
- 25
- 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) = ceiling(n*phi^11), where phi is the golden ratio, A001622.at n=20A004966
- Powers of fifth root of 10 rounded down.at n=18A018141
- Powers of fifth root of 10 rounded to nearest integer.at n=18A018142
- Discriminants of totally real quartic fields.at n=12A023680
- a(n) = (d(n)-r(n))/5, where d = A026060 and r is the periodic sequence with fundamental period (0,0,1,4,0).at n=40A026062
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 42.at n=17A031540
- Denominators of continued fraction convergents to sqrt(636).at n=7A042221
- Nonprime numbers k such that sum of aliquot divisors of k is a cube.at n=26A048698
- a(n) = a(1) + a(2) + ... + a(n-1) + a(m) for n >= 4, where m = 2*n - 2 - 2^(p+1) and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), starting with a(1) = 1, a(2) = 3, and a(3) = 2.at n=11A049971
- Indices of primes in sequence defined by A(0) = 77, A(n) = 10*A(n-1) - 13 for n > 0.at n=12A056259
- Integers for which the periodic part of the continued fraction for the square root of n begins with 10.at n=39A065013
- Numbers k such that k! + (k+1)! - 1 is prime.at n=21A087146
- a(n) = index of the first occurrence of n in A088606.at n=36A088757
- a(n) = 97*n + 101.at n=40A100775
- Largest number whose 5th power has n digits.at n=17A114323
- Number of base 21 circular n-digit numbers with adjacent digits differing by 9 or less.at n=3A125478
- Lucky numbers (A000959) which are congruent to 5 mod 7.at n=41A137187
- a(n) = least m such that sum of m reciprocal primes starting with n-th prime is >1.at n=13A137368
- a(n) = (5*n^2 - 11*n + 8)/2.at n=40A140066
- Complete list of discriminants of definite Eichler orders with class number 2.at n=36A143748