13121
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 8
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 13122
- 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
- 13120
- Möbius Function
- -1
- Radical
- 13121
- 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
- 45
- 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
- 1561
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Class 1+ primes: primes of the form 2^i*3^j - 1 with i, j >= 0.at n=26A005105
- Numbers k such that the continued fraction for sqrt(k) has period 99.at n=9A020438
- Primes that remain prime through 3 iterations of function f(x) = 2x + 9.at n=28A023276
- Primes that remain prime through 3 iterations of function f(x) = 8x + 3.at n=5A023292
- Primes that remain prime through 4 iterations of function f(x) = 2x + 9.at n=11A023306
- Primes that remain prime through 4 iterations of function f(x) = 8x + 3.at n=0A023320
- Numbers whose maximal base-9 run length is 4.at n=23A037999
- Numerators of continued fraction convergents to sqrt(410).at n=3A041778
- Numbers having four 8's in base 9.at n=1A043488
- Numbers whose base-3 representation contains no 0's and exactly one 1.at n=36A044966
- a(0)=1, a(n) = 3*a(n-1) + 2; a(n) = 2*3^n - 1.at n=8A048473
- Primes p from A031924 such that A052180(primepi(p)) = 11.at n=27A052232
- Prime number spiral (clockwise, Northeast spoke).at n=20A054553
- Numbers k such that k^8 == 1 (mod 9^3).at n=35A056084
- Primes p such that x^41 = 2 has no solution mod p.at n=38A059236
- Primes p such that x^16 = 2 has no solution mod p, but x^8 = 2 has a solution mod p.at n=27A059287
- Primes p such that x^48 = 2 has no solution mod p, but x^24 = 2 has a solution mod p.at n=20A059669
- Number of alpha-beta evaluations in a tree of depth n and branching factor b=3.at n=16A060647
- Numbers of the form 3^m - 1 or 2*3^m - 1; i.e., the union of sequences A048473 and A024023.at n=17A062318
- Primes having only {1, 2, 3} as digits.at n=39A062350