2125
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 10
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 2808
- Proper Divisor Sum (Aliquot Sum)
- 683
- 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
- 1600
- Möbius Function
- 0
- Radical
- 85
- Omega Function (Ω)
- 4
- 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
- 125
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
- 9-gonal (or enneagonal or nonagonal) numbers: a(n) = n*(7*n-5)/2.at n=25A001106
- Positions of remoteness 5 in Beans-Don't-Talk.at n=43A005697
- Let S denote the palindromes in the language {0,1,2,3,4}*; a(n) = number of words of length n in the language SS.at n=6A007058
- a(n) = floor(C(n,4)/5).at n=24A011795
- a(n) = floor( n*(n-1)*(n-2)/5 ).at n=23A011887
- a(n) = floor( n*(n-1)*(n-2)/14 ).at n=32A011896
- Numbers k such that the continued fraction for sqrt(k) has period 25.at n=9A020364
- a(n) = Sum_{k = 1..n} k*floor((n + prime(k))/k).at n=28A024929
- a(1) = 5; a(n+1) = a(n)-th nonprime, where nonprimes begin at 1.at n=22A025005
- Numbers that are the sum of 2 nonzero squares in exactly 4 ways.at n=3A025287
- Numbers that are the sum of 2 nonzero squares in 3 or more ways.at n=22A025294
- Numbers that are the sum of 2 nonzero squares in 4 or more ways.at n=3A025295
- Numbers that are the sum of 2 distinct nonzero squares in exactly 4 ways.at n=3A025305
- Numbers that are the sum of 2 distinct nonzero squares in 3 or more ways.at n=21A025313
- Numbers that are the sum of 2 distinct nonzero squares in 4 or more ways.at n=3A025314
- Sequence satisfies T^2(a)=a, where T is defined below.at n=45A027587
- Odd 9-gonal (or enneagonal) numbers.at n=12A028991
- Numbers n such that n divides the (right) concatenation of all numbers <= n written in base 7 (most significant digit on right).at n=10A029500
- Nonsquarefree k such that Pell equation x^2 - k*y^2 = -1 is soluble.at n=19A031397
- Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted then there are a pair of central terms both equal to 4.at n=15A031417