13123
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 10
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 14328
- Proper Divisor Sum (Aliquot Sum)
- 1205
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 11920
- Möbius Function
- 1
- Radical
- 13123
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 2
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
- 76
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- yes
- Squarefree Number
- yes
- Prime Power
- no
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Numbers that are the sum of 7 positive 7th powers.at n=33A003374
- Numbers that are the sum of 3 nonzero 8th powers.at n=7A003381
- Numbers that are the sum of at most 3 nonzero 8th powers.at n=17A004876
- Numbers that are the sum of at most 4 nonzero 8th powers.at n=26A004877
- Positions where A007600 increases.at n=26A007601
- Number of partitions of n into 7 unordered relatively prime parts.at n=47A023027
- a(n) = number of partitions of n into an odd number of parts, the least being 2; also a(n+2) = number of partitions of n into an even number of parts, each >=2.at n=51A027188
- Numbers whose set of base-16 digits is {3,4}.at n=16A032840
- Trajectory of 166 under map x->x + (x-with-digits-reversed).at n=4A033675
- a(n) = 1 + 2*3^(n-1) with a(0)=2.at n=9A052919
- Numbers k such that k^8 == 1 (mod 9^3).at n=36A056084
- a(n) is least odd integer not a partial sum of 1, 3, ..., a(n-1).at n=17A062547
- Second generation sequence in which each number is skipped that can be written as sum of distinct previous entries. To make the first generation we start with all natural numbers: this gives the powers of 2 (A000079). For the second generation we start with the natural numbers from which are removed the numbers of the first generation.at n=17A072134
- Numbers n for which there are exactly twelve k such that n = k + reverse(k).at n=8A072435
- Triangular array T of numbers generated by these rules: 2 is in T; and if x is in T, then 2x-1 and 3x-2 are in T.at n=53A094617
- Number of layers of dough separated by butter in successive foldings of croissant dough.at n=9A100702
- Semiprimes of the form 2*n + 1, where n is a square.at n=34A111351
- Pierpont semiprimes: semiprimes of the form (2^K)*(3^L)+1.at n=30A113432
- Semiprimes (A001358) whose digit reversal is a triangular number.at n=37A115741
- Numbers k such that k and k^2 use only the digits 1, 2, 3, 7 and 9.at n=15A136983