SI prefixes

1e18exaE1,000,000,000,000,000,000one quintillion
1e15petaP1,000,000,000,000,000one quadrillion
1e12teraT1,000,000,000,000one trillion
1e9gigaG1,000,000,000one billion (see note)
1e6megaM1,000,000one million
1e3kilok1,000one thousand
1e2hectoh100one hundred
1e1dekada10ten
1e-1decid0.1one tenth
1e-2centic0.01one hundreth
1e-3millim0.001one thousandth
1e-6micro 0.000,001one millionth
1e-9nanon0.000,000,001one billionth
1e-12picop0.000,000,000,001one trillionth
1e-15femtof0.000,000,000,000,001one quadrillionth
1e-18attoa0.000,000,000,000,000,001one quintillionth
1e-18attoa0.000,000,000,000,000,001one quintillionth

UK billion = 1e12

US billion = 1e9