Question

Which of the following is not a factor of 144?​

Answer 1

Since there is no definite option, the factors of 144 are: 1, 2, 3, 4, 6, 8, 9, 12, 36, 48, 72 and 144 itself. (A number which divides a number is its factor.) So, the numbers which do not divide 144 are not its factors.

More:-

If a number is $N = a^p · b^q...$, that is, can be expressed in form of its factors $a, b, ...$, with indices $p, q, ...$, we can say:-

1. No. of factors = $(p + 1)(q + 1)(r + 1)...$
2. Product of their factors = ${N}^{\frac{Total \ factors}{2}}$
3. Sum of their factors = $\frac{{a}^{p - 1} - 1}{a - 1} \times \frac{{b}^{q - 1} - 1}{b - 1} \times ...$.

If a is a factor of b, then we write b | a.