 
Consider these examples.
 2 thousand is 2,000
 is 2 thousand
 = 2 x 10^{3}

 2 million is 2,000,000
 is 2 thousand thousands = 2 x 10^{3} x 10^{3}
 = 2 x 10^{6}

 2 billion is 2,000,000,000
 is 2 thousand, thousand, thousands = 2 x 10^{3} x 10^{3} x 10^{3}
 = 2 x 10^{9}
 or
 is 2 million thousands
 = 2 x 10^{6} x 10^{3}
 = is 2 x 10^{9}

 2 trillion is 2,000,000,000,000
 is 2 thousand thousand thousand thousand
 = 2 x 10^{3} x 10^{3} x 10^{3} x 10^{3}
 = 2 x 10^{12}
 or
 is 2 billion thousands
 = 2 x 10^{9} x 10^{3}
 = 2 x 10^{12}
 or
 is 2 million, millions
 is 2 x 10^{6} x 10^{6}
 = 2 x 10^{12}

 2 quadrillion is 2,000,000,000,000,000
 is 2 thousand thousand thousand thousand thousand
 = 2 x 10^{3} x 10^{3} x 10^{3} x 10^{3} x 10^{3}
 = 2 x 10^{15}
 or
 is 2 million million thousands
 = 2 x 10^{6} 10^{6} x 10^{3}
 = 2 x 10^{15}
 or
 is 2 million billions
 = 2 x 10^{6} x 10^{9}
 = 2 x 10^{15}

 2 quintillion is 2,000,000,000,000,000,000
 is 2 thousand thousand thousand thousand thousand thousand
 = 2 x 10^{3} x 10^{3} x 10^{3} x 10^{3} x 10^{3} x 10^{3}
 = 2 x 10^{18}
 or
 is 2 trillion million
 is 2 million million millions
 is 2 billion billions
 = 2 x 10^{18}
