11981
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 11982
- 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
- 11980
- Möbius Function
- -1
- Radical
- 11981
- 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
- 50
- 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
- 1437
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- a(0) = 1, a(n) = 11*n^2 + 2 for n>0.at n=33A010003
- Primes that remain prime through 3 iterations of function f(x) = 2x + 9.at n=26A023276
- Primes that remain prime through 4 iterations of function f(x) = 2x + 9.at n=10A023306
- Numerators of continued fraction convergents to sqrt(151).at n=6A041276
- Primes p from A031924 such that A052180(p) = 23.at n=13A052238
- Least prime in A031924 (lesser of 6-twins) such that the distance to the next 6-twin is 2*n.at n=28A052352
- Primes of the form sum 6d/(2 + mu(d)) for some k and all d dividing k.at n=27A069548
- Number of partitions of n into parts but with two kinds of parts of sizes 1 to 10.at n=18A103929
- Primes of the form n^2+5*n+c (n>=0), where c=3 for even n and c=-3 for odd n.at n=24A117012
- Numbers k such that the k-th triangular number contains only digits {1,7,8}.at n=9A119147
- Primes p2 such that p1^2 + p2^3 is an average of twin primes and p1 < p2 are consecutive primes.at n=15A138716
- Primes of the form 210n+11.at n=27A140840
- Primes congruent to 30 mod 37.at n=38A142139
- Primes congruent to 9 mod 41.at n=41A142206
- Primes congruent to 27 mod 43.at n=33A142276
- Primes congruent to 43 mod 47.at n=34A142394
- Primes congruent to 25 mod 49.at n=30A142435
- Primes congruent to 3 mod 53.at n=32A142533
- Primes congruent to 46 mod 55.at n=36A142633
- Primes congruent to 11 mod 57.at n=41A142672