10^37218383881977644441306597687849648128; 10^(7×2^122)
A vast number from the Avatamsaka Sutra, used in Buddhist cosmology to express an unimaginably large quantity. Not used in everyday counting.
The Avatamsaka Sutra features an enormous number called 'fukasetsufukasetsuten'.
From the Chinese translation of the Avatamsaka Sutra; the term is a compound of 不可説 (inexpressible) repeated and followed by 転 (turn, shift), suggesting a number beyond expression.