3980
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 12
- Divisor Sum
- 8400
- Proper Divisor Sum (Aliquot Sum)
- 4420
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 1584
- Möbius Function
- 0
- Radical
- 1990
- Omega Function (Ω)
- 4
- Little Omega Function (ω)
- 3
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
- 25
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
- yes
- Odd
- no
Appears in sequences
- Smallest multiple of n whose digits sum to n.at n=20A002998
- a(n) = floor(n*phi^11), where phi is the golden ratio, A001622.at n=20A004926
- a(n) = round(n*phi^11), where phi is the golden ratio, A001622.at n=20A004946
- Coordination sequence T7 for Zeolite Code MTT.at n=39A008195
- If a, b in sequence, so is ab+7.at n=34A009312
- Coordination sequence for sigma-CrFe, Position Xc.at n=16A009961
- a(n) = A026637(2*n, n-1).at n=6A026639
- a(n) = Sum_{k=0..n-2} T(n,k) * T(n,k+2), with T given by A026626.at n=5A026963
- Numbers k such that 177*2^k+1 is prime.at n=38A032465
- Numbers whose set of base-7 digits is {1,4}.at n=43A032819
- Conjecturally, a power of 2 written in base 3 cannot have this many 0's.at n=30A036462
- Denominators of continued fraction convergents to sqrt(396).at n=7A041753
- Numbers whose base-7 representation contains exactly three 4's.at n=33A043411
- Number of rooted trees with n nodes and 11 leaves.at n=4A055286
- a(n) = Sum_{ r = 0 to n} L(n,r), where L(n,r) (A067049) = lcm(n, n-1, n-2, ..., n-r+1)/lcm(1, 2, 3, ..., r).at n=13A061297
- Numbers k such that prime(k+1)-(k+1)*tau(k+1) = prime(k-1)-(k-1)*tau(k-1) where tau(k) = A000005(k) is the number of divisors of k.at n=29A067335
- Convolution of L(n+1) := A000204(n+1) (Lucas), n>=0, with L(n+9), n>=0.at n=4A067987
- Smallest proper multiple of n with digit sum n.at n=19A069035
- The q expansion of Lambda^5, a Hauptmodul for Gamma_1(5).at n=19A078905
- Triangle T(n,m) read by rows: matrix product A053121 * A038207.at n=38A096164