231 (two hundred
ndthirty-one) is the
natural number
In mathematics, the natural numbers are the numbers 0, 1, 2, 3, and so on, possibly excluding 0. Some start counting with 0, defining the natural numbers as the non-negative integers , while others start with 1, defining them as the positive in ...
following
230 and preceding
232.
Mathematics
* 231 is a
sphenic number.
* 231 is the 21st
triangular number, a
doubly triangular number, a
hexagonal number, an
octahedral number
In number theory, an octahedral number is a figurate number that represents the number of spheres in an octahedron formed from close-packed spheres. The th octahedral number O_n can be obtained by the formula:.
:O_n=.
The first few octahedral ...
and a
centered octahedral number.
* 231 is palindromic in base 2 (11100111
2).
* 231 is the number of integer
partitions of 16.
* The
Mertens function of 231 returns 0.
In other fields
* A
US gallon is defined by being exactly 231 cubic inches, the volume of a cylinder 7 inches in diameter and 6 inches tall, where
is approximated as
.
Religion
* 231 in the
Kabbalistic text
Sefer Yetzirah is identified as the number of “gates” in the Hebrew alphabet, mystical combinations of two unique letters where order is interchangeable.
References
Integers
{{Num-stub