181

181 is the number following 180 and preceding 182^[1].

Properties[]

181 is a centered square number.^[9]
181 is a centered pentagonal number.^[10]
181 is a centered dodecagonal number.^[11]
181 is deficient.^[12]
181 is a palindromic number, meaning it is the same forwards and reverse.^[13]^[14]
181 is a star prime.^[15]

Notation	Lower bound	Upper bound
Up-arrow notation	13 ↑ 2
Scientific notation	1.81 x 10²	1.811 x 10²
Slow-growing hierarchy	\(g_{\omega^{\omega}}(3)\)	\(g_{\omega^{\omega}}(4)\)
Copy notation	1[3]	2[3]
Chained arrow notation	13 → 2
Bowers' Exploding Array Function/Bird's array notation	{13,2}
Fast-growing hierarchy	f₁(89)	f₁(90)
Hardy hierarchy	H_ω(90)	H_ω(91)
Middle-growing hierarchy	m(ω,7)	m(ω,8)
Hyper-E notation	E2.2577
Hyper-E notation (non-10 base)	\(E[13]2\)
Hyperfactorial array notation	5!	6!
X-Sequence Hyper-Exponential Notation	13{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)[13]	(0)[14]
m(n) map	m(1)(3)	m(1)(4)
s(n) map	\(s(1)(\lambda x . x+1)(89)\)	\(s(1)(\lambda x . x+1)(90)\)