16021
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 10
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 16492
- Proper Divisor Sum (Aliquot Sum)
- 471
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 15552
- Möbius Function
- 1
- Radical
- 16021
- 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
- 146
- 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) = (prime(n)^2 + 1)/2.at n=39A066885
- Third row of Pascal-(1,5,1) array A081580.at n=30A081589
- (Prime(prime(n))^2+1)/2.at n=12A092773
- Numbers which are the sum of two positive cubes and divisible by 37.at n=19A102618
- Semiprimes in A103376.at n=19A103396
- Column k=2 sequence of array A103728.at n=40A103729
- Negative numbers written in a bits-of-Pi/primorial base system.at n=34A109839
- Least k such that prime(n)^2 divides binomial(2k,k).at n=40A110494
- Number of solutions to +-p(1)+-p(2)+-...+-p(2n)=1 where p(i) is the i-th prime.at n=10A113040
- Numbers k such that 2^(2k-1) == 2 (mod 2k) and such that 2^(k-1) != 1 (mod k).at n=31A176033
- Exponential transform of (A000275 number of pairs of permutations with rise/rise forbidden).at n=6A188489
- Number of 12X2 integer matrices with each row summing to zero, row elements in nondecreasing order, rows in lexicographically nondecreasing order, and the sum of squares of the elements <= 2*n^2 (number of collections of 12 zero-sum 2-vectors with total modulus squared not more than 2*n^2, ignoring vector and component permutations).at n=11A192713
- Left edge of the triangle in A033291.at n=36A192735
- Numbers k^2 + (k+1)^2 that can be expressed as a sum of two squares in exactly one other way.at n=39A239527
- Numbers n such that the digit sum of Fibonacci(n) is equal to the digit sum of Lucas(n).at n=36A244923
- 26-gonal numbers: a(n) = n*(12*n-11).at n=37A255185
- Numbers n such that (n-1)^3 + (n+1)^3 is a taxi-cab number (A001235).at n=36A272910
- Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f.: exp(Sum_{j>=1} sigma_k(j) * x^j).at n=27A294296
- E.g.f.: exp(Sum_{n>=1} d(n) * x^n), where d(n) is the number of divisors of n.at n=6A294363
- Number of ways of partitioning the set of the first n primes into two subsets whose sums differ at most by 1.at n=22A306443