7213
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 7214
- Proper Divisor Sum (Aliquot Sum)
- 1
- 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
- 7212
- Möbius Function
- -1
- Radical
- 7213
- Omega Function (Ω)
- 1
- Little Omega Function (ω)
- 1
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
- 44
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- yes
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 922
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Smallest positive number that can be written as sum of distinct Fibonacci numbers in n ways.at n=71A013583
- Primes that remain prime through 3 iterations of function f(x) = 5x + 2.at n=14A023283
- a(n) = least k such that 1+2+...+k >= E{1,2,...,n}, where E is the 3rd elementary symmetric function.at n=30A027917
- Numbers k that divide the (left) concatenation of all numbers <= k written in base 11 (most significant digit on left).at n=19A029480
- T(n,n-3), array T as in A038792.at n=35A038793
- a(n)=(s(n)+3)/10, where s(n)=n-th base 10 palindrome that starts with 7.at n=43A043086
- Numbers whose base-5 representation contains exactly three 2's and two 3's.at n=27A045276
- Primes with first digit 7.at n=39A045713
- Discriminants of real quadratic fields with class number 1 and related continued fraction period length of 9.at n=19A050958
- Primes p from A031924 such that A052180(primepi(p)) = 7.at n=37A052231
- Run through primes p; if the digits of p*q (where q is the prime following p) can be rearranged to form one or more primes r, append these primes r to the sequence.at n=35A053736
- Number of collinear triples in a 3 X n rectangular grid.at n=25A057566
- Numbers k such that the sum of odd primes up to k is palindromic.at n=5A058846
- Primes p such that p^12 reversed is also prime.at n=18A059705
- Let p(k) denote k-th prime; consider solutions (n,m) of the Diophantine system {p(p(n)+1)-p(p(n))=2, p(p(n))-6.p(p(m))=-1} (*); sequence gives values of m.at n=26A065511
- a(n) = floor(Pi^n mod n^Pi).at n=18A066434
- Define the composite field of a prime q to be f(q) = (t,s) if p, q, r are three consecutive primes and q-p = t and r-q = s. This is a sequence of primes q with field (2,6).at n=39A073650
- Fourth row of Pascal-(1,3,1) array A081578.at n=9A081586
- Initial members of 25 consecutive primes in a 5 X 5 spiral wherein the mean of all 12 sums is prime.at n=17A094458
- Primes from merging of 4 successive digits in decimal expansion of Catalan's constant.at n=10A104918