1667
domain: N
Properties
Digital Properties
- Digit Count
- 4
- 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
- 1668
- Proper Divisor Sum (Aliquot Sum)
- 1
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 1666
- Möbius Function
- -1
- Radical
- 1667
- 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
- 29
- 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
- 262
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Coefficient of q^(2n-1) in the series expansion of Ramanujan's mock theta function f(q).at n=31A000199
- a(n) = a(n-1) + 3*a(n-2).at n=9A006138
- Number of skeins with vertical symmetry.at n=7A007162
- Coordination sequence T1 for Zeolite Code MON.at n=25A008181
- Coordination sequence T4 for Zeolite Code RSN.at n=27A009888
- Expansion of 1/(1-x^2-x^3-x^4-x^5-x^6).at n=19A013983
- Nine iterations of Reverse and Add are needed to reach a palindrome.at n=3A015990
- Expansion of 1/(1-x^5-x^6-x^7).at n=50A017838
- Powers of fifth root of 22 rounded to nearest integer.at n=12A018178
- Powers of fifth root of 22 rounded up.at n=12A018179
- Numbers k such that the continued fraction for sqrt(k) has period 22.at n=35A020361
- Let q_k=p(p+2) be product of k-th pair of twin primes; sequence gives values of p such that (q_k)^2 > q_{k-i}q_{k+i} for all 1 <= i <= k-1.at n=20A021005
- Primes p such that 7*p + 8 is also prime.at n=48A023226
- Numbers k such that k and 8*k + 1 are both prime.at n=47A023228
- a(n) = 1*t(n) + 2*t(n-1) + ... + k*t(n+1-k), where k=floor((n+1)/2) and t = A002808 (composite numbers).at n=21A023863
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = (natural numbers), t = (composite numbers).at n=20A024860
- a(n) = (d(n)-r(n))/2, where d = A026063 and r is the periodic sequence with fundamental period (1,1,0,1).at n=17A026064
- Numbers whose square has its digits in nondecreasing order.at n=33A028819
- Primes that when squared gives numbers with digits in nondecreasing order.at n=15A028865
- Number of partitions of floor(n^2/2) with at most n parts and maximal height n.at n=9A029895