How many zeros are in one billion written out in full?
Answer9
One billion is 10 to the power 9, which is a 1 followed by nine zeros.
Challenge · Facts & stats
Billionaire facts & stats
7 fact-checked facts about billions and very large numbers, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
Which metric prefix means one billion (10^9)?
AnswerGiga
Giga means 10^9, as in a gigawatt of power or a gigahertz of frequency.
Going deeper
In the traditional long scale, still used in many European languages, what does 'billion' mean?
AnswerA million millions
In the long scale, 'bi-' marks the second power of a million, so a billion is 10^12; British official usage moved to the short scale in the 1970s.
According to the Big Bang model, about how old is the Universe?
Answer13.8 billion years
Measurements of the cosmic microwave background put the age of the Universe at about 13.8 billion years.
About how many neurons are in an adult human brain?
AnswerAbout 86 billion
Careful cell-counting studies estimate the adult human brain contains roughly 86 billion neurons.
Expert level
Which metric prefix means one billionth (10^-9)?
AnswerNano
Nano means 10^-9, so a nanometre is one billionth of a metre.
About how old is planet Earth?
Answer4.54 billion years
Radiometric dating of meteorites and ancient rocks puts Earth's age at about 4.54 billion years.
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