9999
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 36
- Digital Root
- 9
- Palindromic Number
- yes
- Repdigit
- yes
- Automorphic
- no
- Kaprekar Number
- yes
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 12
- Divisor Sum
- 15912
- Proper Divisor Sum (Aliquot Sum)
- 5913
- 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
- 6000
- Möbius Function
- 0
- Radical
- 3333
- Omega Function (Ω)
- 4
- Little Omega Function (ω)
- 3
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
- 91
- 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
- a(n) = 10^n - 1.at n=4A002283
- Denominators of greedy Egyptian fraction for e - 2.at n=3A006525
- Kaprekar numbers: positive numbers n such that n = q+r and n^2 = q*10^m+r, for some m >= 1, q >= 0 and 0 <= r < 10^m, with n != 10^a, a >= 1.at n=16A006886
- Let j = | i - i_written_backwards |, k = j + j_written_backwards; then k is in this sequence.at n=41A008920
- Repdigit numbers, or numbers whose digits are all equal.at n=36A010785
- a(n) = floor( n*(n-1)*(n-2)/25 ).at n=64A011907
- Numbers > 9 with all digits the same.at n=26A014181
- Divisors of 99999999.at n=23A027890
- Divisors of 9999.at n=11A027894
- Numbers k such that k*(k+2) is a palindrome.at n=17A028503
- Palindromes of form k*(k+2); or palindromes 1 less than a square.at n=8A028504
- Palindromic lucky numbers.at n=27A031161
- Lucky numbers that are both palindromic and nonprime.at n=22A031880
- Repdigital lucky numbers.at n=8A031882
- Lucky numbers that are concatenations of a number k with itself.at n=11A032650
- Numbers k such that (k*(k+1)*(k+2)) / (k+(k+1)+(k+2)) is a palindrome.at n=12A032789
- Numbers whose maximal base-10 run length is 4.at n=8A033285
- Trimorphic numbers: n^3 ends with n. Also m-morphic numbers for all m > 5 such that m-1 is not divisible by 10 and m == 3 (mod 4).at n=36A033819
- Largest integer with n digits and exactly n prime factors (counted with multiplicity).at n=3A036337
- Palindromes that start with 9.at n=21A043044