12721
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- yes
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 12722
- Proper Divisor Sum (Aliquot Sum)
- 1
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 12720
- Möbius Function
- -1
- Radical
- 12721
- 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
- 107
- 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
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 1519
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- From the expansion of sinh(x) / cos(x): a(n) = odd part of A002084(n).at n=5A002085
- Palindromic primes: prime numbers whose decimal expansion is a palindrome.at n=26A002385
- Fibonacci sequence beginning 3, 19.at n=15A022128
- Primes that remain prime through 3 iterations of function f(x) = 9x + 4.at n=27A023297
- Primes that remain prime through 4 iterations of function f(x) = 9x + 4.at n=9A023325
- Numbers whose least quadratic nonresidue (A020649) is 13.at n=35A025025
- Odd palindromes in which parity of digits alternates.at n=38A030148
- Palindromic primes in which parity of digits alternates.at n=12A030150
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 80 ones.at n=5A031848
- Lesser of two consecutive palindromes, both of which are prime.at n=7A032593
- Palindromic prime lengths of factorials: see A035067.at n=16A035068
- Primes p such that (p+1)/2 and (p+2)/3 are also primes.at n=30A036570
- Base 4 digits are, in order, the first n terms of the periodic sequence with initial period 3,0,1,2.at n=6A037758
- Palindromic Fibonacci-lucky numbers.at n=48A039674
- Palindromic and prime Fibonacci-lucky numbers.at n=14A039679
- a(n) = least k such that A048825(k) = n.at n=5A048826
- Palindromic primes containing no pair of consecutive equal digits.at n=23A050784
- Palindromic primes whose sum of squared digits is also prime.at n=11A052035
- Primes of the form k(k+1)/2+1 (i.e., central polygonal numbers, or one more than triangular numbers).at n=40A055469
- Primes p such that x^53 = 2 has no solution mod p.at n=25A059258