Question

What is the highest power of 2 that divides 20! completely ?

Answer 1

Highest power of 2 that divides 20!

$=\left[\frac{20}{2}\right]+\left[\frac{20}{4}\right]+\left[\frac{20}{8}\right]+\left[\frac{20}{16}\right]+\left[\frac{20}{32}\right]+....$

$=10+5+2+1+0+0+...$

$=18$