The mathematician Edmund Landau said (translation from German): Number theory is useful, since one can graduate with it.

(from his Foreword to Vorlesungen über Zahlentheorie (Lectures on Number Theory) (1927).)

This from https://en.wikiquote.org/wiki/Edmund_Landau

Not right now... but maybe in the future, who knows. There was a time number theory was viewed as pointless: "The theory of Numbers has always been regarded as one of the most obviously useless branches of Pure Mathematics." - G.H.Hardy.

He might be very disappointed that number theory underpins modern cryptography.

Perhaps the algorithm used to discover the solution may be of application. As is often the case in pure math, the methods used to find solutions to otherwise inconsequential problems later find use years down the line.

If the solutions are that hard to find, you could probably make a commit/ reveal scheme out of it.

Apparently not. It more or less says so in the article.