I need these numbers in scientific notation, please! Thank you!

[tex]\text{The scientific notation:}\\\\a\cdot10^k\ \text{where}\ 1\leq a<10\ \text{and}\ k\in\mathbb{Z}[/tex]
[tex]18.4\ m=1.84\cdot10\ m\\\\0.000000000172\ g=0\underbrace{.0000000001}_{10\to}72=1.72\cdot10^{-10}\ g\\\\4292000\ s=4\underbrace{292000}_{\leftarrow6}\ s=4.292\cdot10^6\ s\\\\8.3\ \cdot10^{-4}\ m\\\\1.496\cdot10^8\ m\\\\23.1\cdot10^{-3}\ kg=2.31\cdot10\cdot10^{-3}\ kg=2.31\cdot10^{-2}\ kg[/tex]