12
domain: N
Properties
Digital Properties
- Digit Count
- 2
- Digit Sum
- 3
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 28
- Proper Divisor Sum (Aliquot Sum)
- 16
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- yes
Derived Values
- Euler's Totient
- 4
- Möbius Function
- 0
- Radical
- 6
- Omega Function (Ω)
- 3
- 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
- yes
- Hexagonal Number
- no
- Lucas Number
- no
- Tetrahedral Number
- no
- Pell Number
- yes
- Tribonacci Number
- no
- Pronic Number
- yes
Recreational
- Happy Number
- no
- Harshad Number
- yes
- Narcissistic Number
- no
- Collatz Steps
- 9
- Smith Number
- no
Classification
- Natural
- yes
- Even
- yes
- Odd
- 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
- yes
- Carmichael Number
- no
Names
- German
- zwölf· ordinal: zwölfte
- English
- twelve· ordinal: twelfth
- Spanish
- doce· ordinal: duodécimo
- French
- douze· ordinal: douzième
- Italian
- dodici· ordinal: 12º
- Latin
- duodecim· ordinal: 12.
- Portuguese
- doze· ordinal: 12º
Appears in sequences
- Number of groups of order n.at n=88A000001
- 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=88A000003
- d(n) (also called tau(n) or sigma_0(n)), the number of divisors of n.at n=59A000005
- d(n) (also called tau(n) or sigma_0(n)), the number of divisors of n.at n=71A000005
- d(n) (also called tau(n) or sigma_0(n)), the number of divisors of n.at n=83A000005
- d(n) (also called tau(n) or sigma_0(n)), the number of divisors of n.at n=89A000005
- d(n) (also called tau(n) or sigma_0(n)), the number of divisors of n.at n=95A000005
- Integer part of square root of n-th prime.at n=34A000006
- Integer part of square root of n-th prime.at n=35A000006
- Integer part of square root of n-th prime.at n=36A000006
- Integer part of square root of n-th prime.at n=37A000006
- Integer part of square root of n-th prime.at n=38A000006
- Number of ways of making change for n cents using coins of 1, 2, 5, 10 cents.at n=11A000008
- Expansion of Product_{m >= 1} (1 + x^m); number of partitions of n into distinct parts; number of partitions of n into odd parts.at n=11A000009
- Euler totient function phi(n): count numbers <= n and prime to n.at n=12A000010
- Euler totient function phi(n): count numbers <= n and prime to n.at n=20A000010
- Euler totient function phi(n): count numbers <= n and prime to n.at n=25A000010
- Euler totient function phi(n): count numbers <= n and prime to n.at n=27A000010
- Euler totient function phi(n): count numbers <= n and prime to n.at n=35A000010
- Euler totient function phi(n): count numbers <= n and prime to n.at n=41A000010