Answer
$23_{10}$ = $10111_{2}$
Work Step by Step
23$\div$2 = 11 remainder r[0] = 1
11$\div$2 = 5 remainder r[1] = 1
5$\div$2 = 2 remainder r[2] = 1
2$\div$2 = 1 remainder r[3] = 0
remainder r[4] = 1
$23_{10}$ = r[4]r[3]r[2]r[1]r[0] = 10111