13781
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
- 4
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 13782
- 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
- 13780
- Möbius Function
- -1
- Radical
- 13781
- 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
- 1630
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Number of positive integers <= 2^n of form x^2 + 16*y^2.at n=17A000018
- Primes p such that the multiplicative order of 2 modulo p is (p-1)/5.at n=35A001135
- Numbers k such that the continued fraction for sqrt(k) has period 39.at n=26A020378
- Primes that remain prime through 3 iterations of function f(x) = 4x + 3.at n=35A023281
- Primes that remain prime through 4 iterations of function f(x) = 4x + 3.at n=9A023311
- Primes that remain prime through 5 iterations of function f(x) = 4x + 3.at n=1A023339
- Incorrect version of A091967.at n=17A031135
- Incorrect version of A107357.at n=17A037181
- Primes p such that x^53 = 2 has no solution mod p.at n=27A059258
- Primes of the form 5k^2 + 5k + 1.at n=27A090562
- a(n) is the n-th term of sequence A_n, ignoring the offset, or -1 if A_n has fewer than n terms.at n=17A091967
- Smallest prime having exactly n representations as a^2+b^2+c^2 with c >= b >= a > 0.at n=39A094714
- Beginning with 2, least prime not occurring earlier such that the concatenation of first n terms has the least prime factor prime(n).at n=24A100759
- Primes by index in A001945.at n=52A104499
- Primes such that the sum of the predecessor and successor primes is divisible by 41.at n=36A113157
- Sequence of primes based on the powers of the golden mean; see formula section for description.at n=12A114345
- Primes p such that p+1, p+2 and p+3 have equal number of divisors.at n=17A119711
- Primes p such that p+1, p+2, p+3 and p+4 have equal number of divisors.at n=1A119728
- Primes p such that p+1, p+2, p+3, p+4 and p+5 have equal number of divisors.at n=0A119730
- Smallest prime divisor of 10*T(n)+1 = 5*n*(n+1)+1, where T(n) = 1 + 2 + ... + n.at n=51A125239