US real estate mogul and presidential contender Donald Trump spent the day campaigning in New Hampshire on Wednesday a day after announcing his presidential bid.

"I'm very competent, and I'm really good at business, and I can make this country so rich and so great again," Trump said, speaking to a crowd at Manchester Community College.

"Maybe (people) don't like my hair... which is real by the way," Trump added. He then asked a woman on stage to prove it.

She took a close look and said "It's thin, but its real."

The billionaire, widely seen as having almost no chance of winning the nomination, brings an outsized personality and a penchant for controversy to an unusually large group of Republicans vying for the presidency.

Trump, who owns several hotels and hosts the reality show "The Celebrity Apprentice" on NBC, boasted having $8.7 billion in net worth, a number he says he released so that America understands he is not a loser.

He has flirted with the notion of running in past elections, but has ultimately backed out each time. This time, he said, the United States needs him to come to the rescue and revive a "dead" American dream.