Heptlastillion is equal to 103*1021.[1] The term was coined by Aarex Tiaokhiao.


Notation Lower bound Upper bound
Arrow notation \(1000\uparrow10\uparrow21\)
Down-arrow notation \(1000\downarrow\downarrow8\)
Steinhaus-Moser Notation 16[3][3] 17[3][3]
Copy notation 2[2,4] 3[3[22]]
H* function H(999H(5)) H(H(6))
Taro's multivariable Ackermann function A(3,A(3,70)) A(3,A(3,71))
Pound-Star Notation #*((1))*(3,0,6)*3 #*((1))*(3,3)*6
BEAF {1000,{10,21}}
Hyper-E notation E(3E21)
Bashicu matrix system (0)(1)[8] (0)(1)[9]
Hyperfactorial array notation (21!)! (22!)!
Fast-growing hierarchy \(f_2(f_2(67))\) \(f_2(f_2(68))\)
Hardy hierarchy \(H_{\omega^22}(67)\) \(H_{\omega^22}(68)\)
Slow-growing hierarchy \(g_{\omega^{\omega^{\omega2+1}3}}(10)\)


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