Four numbers are chosen at random from $\left\{1,2,3,4,...,40\right\}$. The probability that they are not consecutive is

The set of given numbers is $\left\{1,2,3,4,...,40\right\}$

The random experiment is selecting 4 numbers from the given set of numbers

Let $S$ be the sample space, $n\left(S\right)={40}_{C_4}$

Let $E$ be the event of getting four consecutive numbers $n\left(E\right)=37$

Hence, the probability of getting four consecutive numbers is $P\left(E\right)=\frac{n\left(E\right)}{n\left(S\right)}=\frac{37}{{40}_{C_4}}=\frac{37·24}{40·39·38·37}=\frac{1}{2470}$

Therefore, the probability of not getting four consecutive numbers is $1-\frac{1}{2470}=\boxed{\frac{2469}{2479}}$