1,000,000,000 (alternately known as one thousand million and one billion, see below) is the natural number following 999,999,999 and preceding 1,000,000,001.
In modern ('short scale') English language usage, it is usually called a billion (although in many other languages and 'long scale' usage, a billion means a million millions (or 1,000,000,000,000), instead of a thousand millions).
The term milliard can also be used to refer to 1,000,000,000, though this terminology is rarely used in the English language, but often in other languages.
Physical quantities can be expressed using the SI prefixgiga.
9814072356 - largest square pandigital number, largest pandigital pure power
9876543210 - largest pandigital number without redundant digits
Sense of scale
The facts below give a sense of how large 1,000,000,000 (109) is in the context of time:
109 seconds is about 31.7 years.
About 109 minutes ago, the Roman Empire was flourishing. (109 minutes is roughly 1,900 years.)
About 109 hours ago, modern human beings and their ancestors were living in the Stone Age (more precisely, the Middle Paleolithic). (109 hours is roughly 114,000 years.)
About 109 days ago, Australopithecus, an ape-like creature related to an ancestor of modern humans, roamed the African savannas. (109 days is roughly 2.7 million years.)
About 109 months ago, dinosaurs walked the earth during the late Cretaceous. (109 months is roughly 82 million years.)
A is a cube; B consists of 1000 cubes of type A. C consists of 1000 Bs; and D 1000 Cs. Thus there are 1 million As in C; and 1,000,000,000 As in D. Likewise, there are 1,000,000,000 cubic millimeters in a cubic meter.