President Trump’s first days in office promise great things — for job creation and economic renewal overall.

It will be a shame if his auspicious agenda falls through because of an infantile way with numerical nonsense to feed his ego.

Before Trump goes looking for “millions” of “illegal” votes for Hillary Clinton, let him first find the phantom 26 feet of 40 Wall St., his downtown skyscraper.

In a conversation I had with Trump years ago, after 9/11 but before new World Trade Center buildings went up, he claimed that 40 Wall St. — “and I say this sadly” — was, since the terrorist attack, “the tallest building downtown.”

When I demurred that in fact, a nearby building, 70 Pine St., was 25 feet taller than 40 Wall, Trump insisted: “No, my building is taller.”

I politely pointed out that, a) public records clearly state that 70 Pine tops out at 952 feet, compared with 40 Wall’s 927 feet, and, b) you can just look up at the sky and see.

Trump’s dig-in, double-down response: “No, my building is taller. Much taller.”

I moved on. I had a story to write unrelated to 40 Wall St., and no time to argue with him.

Every journalist who’s covered Trump will tell a similar tale.

Something in the mind, personality or soul of Donald J. Trump won’t allow easily verified facts to intrude on his bottomless need for numerical self-justification.

It was almost amusing when Trump was a mere real estate mogul and TV star. Ha ha, that’s Donald being Donald!

But it’s a different story with legislators, judges and heads of state, who won’t be so easily conscripted into Trump’s go-along-to-get-along supporting army.

Nor will the American public sit still for demonstrably fake statistics in matters of grave importance — such as in war, where the taste for bogus “body counts” expired in Vietnam.

Donald, give up this stupid “illegal votes” probe and concentrate on the job you were elected to do — legally.