16621
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 16
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 18144
- Proper Divisor Sum (Aliquot Sum)
- 1523
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 15100
- Möbius Function
- 1
- Radical
- 16621
- 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
- 66
- 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
- Decimal part of a(n)^(1/3) starts with reversal of its integer part: first term of runs.at n=23A034309
- Composite numbers whose prime factors contain no digits other than 1 and 5.at n=23A036305
- Smallest integer k such that 2^n is the largest power of two that is contained in 2^k as a proper substring.at n=26A046300
- Number of polyominoes with n cells that tile the plane by translation.at n=14A075198
- TrueSoFar number of terms in other bases.at n=15A102844
- a(n) = n^5 - 31*n + 31, with n*a(n) + n*( n - 1 )*31 = n^6.at n=6A107255
- Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (-1, 1, 0), (0, 0, -1), (0, 1, 1), (1, -1, 0)}.at n=9A148817
- Nonprime numbers with all divisors starting and ending with digit 1.at n=31A208261
- Number of ordered triples (i,j,k) with |i|, |j|, |k|, |i*j*k| <= n.at n=34A226359
- Values of n such that L(14) and N(14) are both prime, where L(k) = (n^2+n+1)*2^(2*k) + (2*n+1)*2^k + 1, N(k) = (n^2+n+1)*2^k + n.at n=40A227517
- Number of length n+4 0..2 arrays with some pair in every consecutive five terms totalling exactly 2.at n=4A246886
- T(n,k)=Number of length n+4 0..k arrays with some pair in every consecutive five terms totalling exactly k.at n=19A246892
- Number of length 5+4 0..n arrays with some pair in every consecutive five terms totalling exactly n.at n=1A246897
- Composite numbers k with its divisors having the property that the last digit of every divisor is the same as the first digit of the next divisor.at n=34A307858
- a(n) is the exponent of the least power of 2 such that the concatenated digits of the decimal expansion of 2^n are a proper substring of the concatenated digits of the decimal expansion of 2^a(n).at n=26A342575