Ariana Grande's grandpa is her idol.

The 21-year-old pop princess rushed to be at her grandpa's side last week, as he battles cancer in hospital. Keeping her social media followers updated with a series of pictures of her ill grandfather, Ariana was pleased to hear one fan declare Grandpa Grande was her idol.

"Mine too," Ariana posted in response to Twitter user gbiebergomez's sentiment.

Ariana has had a jam-packed weekend and made British history when her new single Problem featuring Iggy Azalea became the first UK number one on sales and streaming.

As of last week the Official Singles Chart now includes data from streaming services such as Spotify, as well as physical and digital sales.

"was too much to fit in one tweet! thank u so much UK, just heard the news today.... love u more than words," Ariana gushed on Twitter.

"adding on to that... i'll try my hardest to reschedule my trip out there! can't thank u enough for ur understanding during this time. love u (sic)."

Ariana has cleared her schedule so she can be on hand to help at her Grandpa's bedside, who's receiving treatment at a hospital in her native Boca Raton in Florida.

Seeing as he's a big fan of the new track, the news was even sweeter for the Right There singer.

"grandpa says his favorite song of mine is "promise"..... I think he means "problem"..... he likes the saxophone (sic)," she added.

Her manager Scooter Braun, who also looks after Justin Bieber, was also overjoyed with the achievement.

"Landing her first Number 1 on the Official Singles Chart is an incredible achievement and another benchmark in the continued global success of Problem.

"Thanks to the loyal UK fans whose incredible support has made this possible. This is your Number 1, too," Scooter told