13721
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 14
- Digital Root
- 5
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 13722
- 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
- 13720
- Möbius Function
- -1
- Radical
- 13721
- 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
- 63
- 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
- 1623
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Numbers k such that 39*2^k + 1 is prime.at n=38A002269
- Number of partitions of n with equal nonzero number of parts congruent to each of 1 and 2 (mod 5).at n=49A035566
- Replace n with concatenation of its divisors.at n=20A037278
- Replace n with concatenation of its odd divisors.at n=20A037283
- Replace n with concatenation of its odd divisors.at n=41A037283
- Replace 2n+1 with concatenation of its divisors.at n=10A037286
- Lesser of irregular twin primes.at n=40A060012
- Lesser of twin primes whose average is 6 times a prime.at n=34A060213
- Primes p = prime(k) such that prime(k) + prime(k+5) = prime(k+1) + prime(k+4) = prime(k+2) + prime(k+3).at n=38A064101
- Records in A079384.at n=9A079385
- Leading term of n-th row of A081491.at n=35A081490
- Smallest member of a pair of consecutive twin prime pairs that have two primes between them.at n=37A089634
- Smallest prime of the form 1 followed by a perfect power.at n=14A089773
- Seventh diagonal (m=6) of triangle A084938; a(n) = A084938(n+6,n) = (n^6 + 45*n^5 + 925*n^4 + 11475*n^3 + 92314*n^2 + 413640*n)/720.at n=6A090392
- Primes arising in A090504.at n=2A090505
- a(n) is the smallest initial value (a prime) for the Euclid-Mullin (EM) sequence in which the p=5 prime emerges as n-th term, i.e., arises at the n-th position.at n=29A093782
- Primes prime(k) such that (prime(k-1) + prime(k+1) + prime(k+2))/prime(k) = 3.at n=26A094933
- Primes such that the sum of the predecessor and successor primes is divisible by 43.at n=38A113158
- Primes of the form 2^a * 5^b * 7^c + 1 for positive a, b, c.at n=9A114992
- a(n) = 104*n + 9977.at n=36A126978