Chapter 4 - Number Representation and Calculation - 4.1 Our Hindu-Arabic System and Early Positional Systems - Exercise Set 4.1 - Page 218: 57

$15,842,203$

Using the table and that the place values are $1,20,18\cdot20=360,18\cdot20^2=7200,18\cdot20^3=144000, 18\cdot20^4=2,880,000$: The numerical value as a Hindu- Arabic numeral is: $5\cdot2,880,000+10\cdot144000+0\cdot7200+6\cdot360+2\cdot20+3\cdot1=14,400,000+1,440,000+0+2160+40+3=15,842,203$