181 (number) explained
Number: | 181 |
Factorization: | prime |
Prime: | 42nd |
Divisor: | 1, 181 |
181 (one hundred [and] eighty-one) is the natural number following 180 and preceding 182.
In mathematics
181 is prime, and a palindromic,[1] strobogrammatic,[2] and dihedral number[3] in decimal. 181 is a Chen prime.[4]
181 is a twin prime with 179,[5] equal to the sum of five consecutive prime numbers:[6] 29 + 31 + 37 + 41 + 43.
181 is the difference of two consecutive square numbers 912 – 902,[7] as well as the sum of two consecutive squares: 92 + 102.[8]
As a centered polygonal number,[9] 181 is:181 is also a centered (hexagram) star number, as in the game of Chinese checkers.
inside a
prime reciprocal magic square repeat
180 digits with a
magic sum
of 810; this value is one less than
811, the
141st prime number and
49th full reptend prime (or equivalently
long prime) in decimal whose reciprocal
repeats 810 digits. While the first full non-normal prime reciprocal magic square is based on
with a magic constant of
81 from a
square,
[12] a normal
magic square has a magic constant
;
[13] the next such full, prime reciprocal magic square is based on multiples of the reciprocal of 383 (also
palindromic).
[14] 181 is an undulating number in ternary and nonary numeral systems, while in decimal it is the 28th undulating prime.[15]
In other fields
181 is also:
External links
Notes and References
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- 2016-05-26 .
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- 2016-05-26.
- Web site: Sloane, N. J. A. . Neil Sloane . Centered polygonal numbers . . OEIS Foundation . 2023-11-02 .
- 2023-11-02 .
- 2023-11-02 .
- Book: Andrews, William Symes . Magic Squares and Cubes . . Chicago, IL . 1917 . 176, 177 . 9780486206585 . 1136401 . 1003.05500 . 0114763 .
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- 2023-09-04 .
- 2023-11-02 .