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121 is the number following 120 and preceding 122[1].

Properties[]

  • 121 is a central polygonal number.[10]
  • 121 is a centered octagonal number.[11]
  • 121 is a centered dodecagonal number.[12]
  • 121 is deficient.[13]
  • Its prime factorization is 112.
  • 121 is a palindromic number, meaning it is the same forwards and reverse.[14][15]


Approximations[]

Notation Lower bound Upper bound
Up-arrow notation 11 ↑ 2
Scientific notation 1.21 x 102 1.211 x 102
Slow-growing hierarchy \(g_{\omega^{\omega}}(3)\) \(g_{\omega^{\omega}}(4)\)
Copy notation 1[3] 2[3]
Chained arrow notation 11 → 2
Bowers' Exploding Array Function/Bird's array notation {11,2}
Fast-growing hierarchy f1(59) f1(60)
Hardy hierarchy Hω(60) Hω(61)
Middle-growing hierarchy m(ω,6) m(ω,7)
Hyper-E notation E2.0828
Hyper-E notation (non-10 base) \(E[11]2\)
Hyperfactorial array notation 5! 6!
X-Sequence Hyper-Exponential Notation 11{1}2
Steinhaus-Moser Notation 3[3] 4[3]
PlantStar's Debut Notation [1] [2]
H* function H(-0.4) H(-0.3)
Bashicu matrix system with respect to version 4 (0)[11] (0)[11]
m(n) map m(1)(3) m(1)(4)
s(n) map \(s(1)(\lambda x . x+1)(59)\) \(s(1)(\lambda x . x+1)(60)\)

Sources[]