Question

Which of the following numbers have exactly 12 factors?

• A. 1220
• B. 610
• C. 300
• D. 1800

Answer 1

The correct option is A

1220

$1220=2\times 2\times 5\times 61$ and thus, 1220 has $(2+1)(1+1)(1+1)=12$ factors in all.
$610=2\times 5\times 61$ and thus, 610 has $(1+1)(1+1)(1+1)=8$ factors in all.
$300=2\times 2\times 5\times 5\times 3$ and thus, 300 has $(2+1)(2+1)(1+1)=18$ factors in all.
$1800=2\times 2\times 2\times 3\times 3\times 5\times 5$ and thus, 1220 has $(3+1)(2+1)(2+1)=36$ factors in all.

Hence, 1220 is the right option.