7950
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 24
- Divisor Sum
- 20088
- Proper Divisor Sum (Aliquot Sum)
- 12138
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 2080
- Möbius Function
- 0
- Radical
- 1590
- Omega Function (Ω)
- 5
- Little Omega Function (ω)
- 4
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
- 52
- 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
- yes
- Odd
- no
Appears in sequences
- Number of 9's in all partitions of n.at n=39A024793
- Sum of the first n palindromes (A002113).at n=47A046489
- Even numbers seen in decimal expansion of Pi (disregarding the decimal period) contiguous, smallest and distinct.at n=11A050818
- Numbers k such that floor(Pi^k) is prime.at n=9A059792
- Values of m such that N=(am+1)(bm+1)(cm+1) is a 3-Carmichael number (A087788), where a,b,c = 1,2,9.at n=13A064241
- Numbers m such that N=(am+1)(bm+1)(cm+1) is a 3-Carmichael number (A087788), where a,b,c = 1,2,19.at n=0A064246
- Values of m such that N=(am+1)(bm+1)(cm+1) is a 3-Carmichael number (A087788), where a,b,c = 1,2,27.at n=4A064250
- a(n) = 60*n^2 + 180*n + 150.at n=9A069477
- At these values of k the first, 2nd and 3rd cyclotomic polynomials all give prime numbers.at n=30A070020
- Third differences of fifth powers (A000584).at n=12A101096
- Values of y in x^2 - 49 = 2*y^2.at n=13A106526
- Average of twin-prime pairs for pairs that are expressible as the sum of two triangular numbers.at n=19A117313
- Numbers n such that n is divisible by (3*s(n)*s(n)+2), where s(n) = sum of digits of n.at n=29A134556
- Even numbers in the decimal expansion of Pi, contiguous and shortest.at n=13A164524
- a(0) = -1, otherwise a(n) = (-1)^n*(n^3 - 15*n^2 + 2*n - 12)/6.at n=42A173248
- Partials sums of A001694.at n=38A174172
- Triangle read by rows: T(n,k) is the number of permutations of [n] having k adjacent cycles (0 <= k <= n). An adjacent cycle is a cycle of the form (i, i+1, i+2, ...) (including 1-element cycles).at n=49A184184
- Number of 6-element nondividing subsets of {1, 2, ..., n}.at n=23A187493
- Number of (w,x,y,z) with all terms in {1,...,n} and w <= harmonic mean of {x,y,z}.at n=12A212104
- a(0)=-4, a(1)=5; thereafter a(n) = 2*a(n-1) + a(n-2).at n=10A221174