7421
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 14
- Digital Root
- 5
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 7644
- Proper Divisor Sum (Aliquot Sum)
- 223
- 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
- 7200
- Möbius Function
- 1
- Radical
- 7421
- 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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 119
- 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
- Pentagonal numbers written backwards.at n=29A004163
- Greatest k such that binomial(k,n) has fewer than n distinct prime factors.at n=39A005735
- Expansion of e.g.f. exp(x)*cosh(log(1+x)).at n=8A009281
- Pseudoprimes to base 31.at n=30A020159
- Pseudoprimes to base 42.at n=22A020170
- Pseudoprimes to base 59.at n=33A020187
- Pseudoprimes to base 74.at n=35A020202
- Strong pseudoprimes to base 42.at n=7A020268
- Strong pseudoprimes to base 59.at n=12A020285
- Strong pseudoprimes to base 74.at n=15A020300
- Numbers k such that the continued fraction for sqrt(k) has period 29.at n=17A020368
- [ (4th elementary symmetric function of S(n))/(2nd elementary symmetric function of S(n)) ], where S(n) = {first n+3 odd positive integers}.at n=15A024205
- Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 34.at n=1A031622
- a(n) = (2*n+1)*(9*n+1).at n=20A033573
- Partial sums of A048654.at n=9A048745
- a(n) = Sum_{m=1..n, k=1..m} T(m,k), array T as in A049834.at n=38A049836
- 11-gonal (or hendecagonal) numbers: a(n) = n*(9*n-7)/2.at n=41A051682
- Discriminants of real quadratic fields with class number 2 and related continued fraction period length of 13.at n=17A051978
- Dimension of the space of weight n cuspidal newforms for Gamma_1( 83 ).at n=26A063356
- Let P(k) = floor(k/2). Start with n, apply P repeatedly until reach 1. a(n) = concatenation of numbers obtained.at n=13A083177