7
domain: N
Properties
Digital Properties
- Digit Count
- 1
- Digit Sum
- 7
- Digital Root
- 7
- Palindromic Number
- yes
- Repdigit
- yes
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 0
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 8
- 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
- 6
- Möbius Function
- -1
- Radical
- 7
- 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
- yes
- Tetrahedral Number
- no
- Pell Number
- no
- Tribonacci Number
- yes
- Pronic Number
- no
Recreational
- Happy Number
- yes
- Harshad Number
- yes
- Narcissistic Number
- yes
- Collatz Steps
- 16
- Smith Number
- no
Classification
- Natural
- yes
- Even
- no
- Odd
- yes
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- yes
- Mersenne Prime
- yes
- Sophie Germain Prime
- no
- Safe Prime
- yes
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 4
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Names
- German
- sieben· ordinal: siebte
- English
- seven· ordinal: seventh
- Spanish
- siete· ordinal: séptimo
- French
- sept· ordinal: septième
- Italian
- sette· ordinal: settimo
- Latin
- septem· ordinal: septimus
- Portuguese
- sete· ordinal: sétimo
Appears in sequences
- Number of classes of primitive positive definite binary quadratic forms of discriminant D = -4n; or equivalently the class number of the quadratic order of discriminant D = -4n.at n=70A000003
- d(n) (also called tau(n) or sigma_0(n)), the number of divisors of n.at n=63A000005
- Integer part of square root of n-th prime.at n=15A000006
- Integer part of square root of n-th prime.at n=16A000006
- Integer part of square root of n-th prime.at n=17A000006
- Number of ways of making change for n cents using coins of 1, 2, 5, 10 cents.at n=8A000008
- Smallest prime power >= n.at n=5A000015
- Smallest prime power >= n.at n=6A000015
- Number of primitive permutation groups of degree n.at n=6A000019
- Number of primitive permutation groups of degree n.at n=7A000019
- Number of primitive permutation groups of degree n.at n=22A000019
- Number of primitive permutation groups of degree n.at n=25A000019
- Number of primitive permutation groups of degree n.at n=31A000019
- Number of primitive permutation groups of degree n.at n=65A000019
- Number of primitive permutation groups of degree n.at n=67A000019
- Number of positive integers <= 2^n of form x^2 + 10 y^2.at n=4A000024
- Coefficients of the 3rd-order mock theta function f(q).at n=7A000025
- Mosaic numbers or multiplicative projection of n: if n = Product (p_j^k_j) then a(n) = Product (p_j * k_j).at n=6A000026
- The positive integers. Also called the natural numbers, the whole numbers or the counting numbers, but these terms are ambiguous.at n=6A000027
- Let k = p_1^e_1 p_2^e_2 p_3^e_3 ... be the prime factorization of n. Sequence gives k such that the sum of the numbers of 1's in the binary expansions of e_1, e_2, e_3, ... is odd.at n=4A000028