How big is a millinillion

"Millinillion" is not a standard term in mathematical nomenclature. You might be thinking of "millillion" or possibly confused about the systematic naming convention for large numbers. The standard Latin-based naming system extends through vigintillion (10^63), centillion (10^303), and can theoretically continue, but there's no recognized "millinillion" in formal mathematics.

If you meant "millillion," this also isn't standard—the system goes: thousand, million, billion, trillion, quadrillion, quintillion... continuing with Latin number prefixes. If you're curious about what comes after numbers like vigintillion or centillion, the Latin-based system can theoretically extend indefinitely (uncentillion, ducentillion, etc.), though names beyond centillion are rarely if ever used. For genuinely large numbers, mathematics uses notation systems rather than names: scientific notation (10^x), arrow notation (Knuth's up-arrows), or specific named constants like googol or Graham's number. If you encountered "millinillion" in a specific source, it might be a creative or informal term not part of standard mathematical nomenclature. For actual large numbers, stick with recognized terms or simply use scientific notation.