Q55 / 160 · TS EAMCET 2018 (04 May Shift 2) · Mathematics
The number of proper divisors of the number obtained by dividing 13 ! with 100 is
- A216
- Correct answerB430
- C214
- D790
Solution
$$
13 !=2 \times 3 \times 4 \times 5 \times 6 \times 7 \times 8 \times 9 \times 10 \times 11 \times 12 \times 13
$$
13 ! is divided by 100
Then, $\frac{13 !}{100}=2^8 \times 3^5 \times 7^1 \times 11^1 \times 13^1$
The number of proper divisor at the number obtained is $(8+1)(5+1)(1+1)(1+1)(1+1)-2$
$$
=9 \times 6 \times 2 \times 2 \times 2-2=432-2=430
$$
Hence, the correct answer is option: 'B'.