What is thousand million?

Answer 1

A thousand million million is 10^3 x 10^6 x 10^6 = 10^15

In those countries that use the long scale (based on powers of a million), eg Europe:

10^15 = 10^3 x (10^6)^2 = a thousand billion, or a billiard.

In those countries that use the short scale (based on powers of a thousand plus one), eg USA:

10^15 = (10^3)^5 = (10^3)^(4+1) = a quadrillion.

To end the confusion a Greek-based system of numbering has been proposed that would call a thousand million million a pentillion,but so far this mathematical compromise is pie in the sky.

Luckily there is an International System of Units (SI, for short) having prefixes that all countries agree on, but you need to affix the prefix to a noun so its use is limited. The SI prefix for quadrillion/billiard is peta-. You can, for example, call 10 to the 15th herz (cycles per second of a sine wave, such as a musical tone), a petahertz.

Answer 2

A billion.