Which symbol indicates a quantity of 1,000,000 in the SI system?

The symbol that indicates a quantity of 1,000,000 in the SI system is "Mega" (M). In the International System of Units (SI), the prefix "Mega" is used to denote one million, or (10^6). This is crucial in fields such as engineering and science where large quantities or measurements need to be conveyed efficiently.

For instance, when discussing data storage, a megabyte (MB) represents one million bytes, making it a common reference point. Understanding this prefix helps in interpreting and converting measurements, as well as in communicating values clearly in technical discussions.

The other prefixes have different meanings; "Kilo" refers to one thousand ((10^3)), "Giga" represents one billion ((10^9)), and "Deca" indicates ten ((10^1)). Knowing these differences is essential for accurately working with and interpreting quantities across various scientific and technical contexts.