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221 is the number following 220 and preceding 222[1].

Properties[]

  • 221 is a centered square number.[10]
  • 221 is deficient.[11]
  • Its prime factorization is 131 × 171.


Approximations[]

Notation Lower bound Upper bound
Up-arrow notation 15 ↑ 2
Scientific notation 2.21 x 102 2.211 x 102
Slow-growing hierarchy \(g_{\omega^{\omega}}(3)\) \(g_{\omega^{\omega}}(4)\)
Copy notation 1[3] 2[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 Hω(110) Hω(111)
Middle-growing hierarchy m(ω,7) m(ω,8)
Hyper-E notation E2.3444
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)[14] (0)[15]
m(n) map m(1)(3) m(1)(4)
s(n) map \(s(1)(\lambda x . x+1)(109)\) \(s(1)(\lambda x . x+1)(110)\)

Sources[]