231

231 is the number following 230 and preceding 232^[1].

Properties[]

Its factors are 1, 3, 7, 11, 21, 33, 77 and 231, making it a composite number.^[2]^[3]^[4] It is also a squarefree number.^[5]
231 is an odd number^[6]^[7] .
231 is an unhappy number.^[8]^[9]

231 is a triangular number.^[10]
231 is a hexagonal number.^[11]
231 is a quadruple factorial.^[12]
231 is deficient.^[13]
Its prime factorization is 3¹ × 7¹ × 11¹.
231 is the 15th partition number^[14] and the 21st triangular number.^[15]
Since 21 is the 6th triangular number, 6 the 3rd triangular number, and 3 the 2nd triangular number, it also appears in the calculation of the triangrol, the triangoogol and the triangrolplex.^[16]
Furthermore, it is the number of cubic inches in a U.S. gallon.^[17]

Notation	Lower bound	Upper bound
Up-arrow notation	15 ↑ 2
Scientific notation	2.31 x 10²	2.311 x 10²
Slow-growing hierarchy	\(g_{\omega^{\omega}}(3)\)	\(g_{\omega^{\omega}}(4)\)
Copy notation	2[3]	3[3]
Chained arrow notation	15 → 2
Bowers' Exploding Array Function/Bird's array notation	{15,2}
Fast-growing hierarchy	f₂(5)	f₂(6)
Hardy hierarchy	H_ω(115)	H_ω(116)
Middle-growing hierarchy	m(ω,7)	m(ω,8)
Hyper-E notation	E2.3636
Hyper-E notation (non-10 base)	\(E[15]2\)
Hyperfactorial array notation	5!	6!
X-Sequence Hyper-Exponential Notation	15{1}2
Steinhaus-Moser Notation	3[3]	4[3]
PlantStar's Debut Notation	[1]	[2]
H* function	H(-0.3)	H(-0.2)
Bashicu matrix system with respect to version 4	(0)[15]	(0)[16]
m(n) map	m(1)(3)	m(1)(4)
s(n) map	\(s(1)(\lambda x . x+1)(114)\)	\(s(1)(\lambda x . x+1)(115)\)