251
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 8
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 252
- 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
- 250
- Möbius Function
- -1
- Radical
- 251
- 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
- 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
- 65
- Smith Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- yes
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 54
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Names
- German
- zweihunderteinundfünfzig· ordinal: zweihunderteinundfünfzigste
- English
- two hundred fifty-one· ordinal: two hundred fifty-first
- Spanish
- doscientos cincuenta y uno· ordinal: 251º
- French
- deux cent cinquante et un· ordinal: deux cent cinquante et unième
- Italian
- duecentocinquantuno· ordinal: 251º
- Latin
- ducenti quinquaginta unus· ordinal: 251.
- Portuguese
- duzentos e cinquenta e um· ordinal: 251º
Appears in sequences
- Let A(n) = #{(i,j,k): i^2 + j^2 + k^2 <= n}, V(n) = (4/3)Pi*n^(3/2), P(n) = A(n) - V(n); sequence gives values of n where |P(n)| sets a new record.at n=15A000092
- Partitions into non-integral powers (see Comments for precise definition).at n=7A000234
- Number of trees with n nodes, 3 of which are labeled.at n=3A000269
- Number of partitions into non-integral powers.at n=4A000347
- Primes p == 3, 9, 11 (mod 20) such that 2p+1 is also prime.at n=8A000355
- Let A(n) = #{(i,j,k): i^2 + j^2 + k^2 <= n}, V(n) = (4/3)*Pi*n^(3/2), P(n) = A(n) - V(n); A000092 gives values of n where |P(n)| sets a new record; sequence gives A(A000092(n)).at n=5A000413
- Number of tournaments on n nodes determined by their score vectors.at n=11A000570
- Primes with 6 as smallest primitive root.at n=4A001125
- Primes p such that the multiplicative order of 2 modulo p is (p-1)/5.at n=0A001135
- Numbers that are the sum of 3 nonnegative cubes in more than 1 way.at n=1A001239
- Numbers that are the sum of 4 cubes in more than 1 way.at n=8A001245
- Table T(n,k) in which n-th row lists prime factors of 2^n + 1 (n >= 0), with repetition.at n=58A001269
- Generalized Stirling numbers, [n+7,7]_5.at n=2A001722
- Primes p such that the congruence 2^x = 5 (mod p) is solvable.at n=30A001916
- A Beatty sequence: floor(n * (sqrt(5) + 3)).at n=47A001962
- Prime determinants of forms with class number 2.at n=26A002052
- Primes of the form 4*k + 3.at n=28A002145
- Smallest prime p==3 (mod 8) such that Q(sqrt(-p)) has class number 2n+1.at n=3A002148
- Smallest primitive factor of 2^(2n+1) + 1.at n=12A002185
- Primes of the form 2^q*3^r*5^s + 1.at n=21A002200