LAKELAND — When high school student Zach Sobiech learned he didn’t have much longer to live, his mother suggested he write letters to tell his loved ones goodbye. Instead, the Minnesota teenager turned to writing music — and his farewell song, “Clouds,” became a YouTube sensation that has attracted more than 4 million views.

Other musicians have covered the tune, and it inspired a celebrity video on YouTube. “Clouds” was even listed No. 1 on the iTunes Top 10 list on Wednesday — two days after Sobiech died after battling bone cancer.

His mother, Laura Sobiech, said on the CaringBridge website that her son was surrounded by family and his girlfriend when he died at his home in Lakeland, an eastern suburb of St. Paul. He had recently turned 18.

Sobiech was being remembered not only for his music, but also for the way he lived. John Hallberg, the chief executive of the Children’s Cancer Research Fund, said Wednesday that Sobiech had a positive attitude and approached his diagnosis with strength and grace.

“You don’t have to find out you’re dying to start living,” Sobiech said in a short video about him titled, “My Last Days: Meet Zach Sobiech,” which also has been viewed more than 4 million times since it was posted to YouTube two weeks ago.

“I want to be remembered as a kid who went down fighting and didn’t really lose,” he said.

Sobiech was diagnosed with osteosarcoma in November 2009. He went through surgeries and chemotherapy and spent some time cancer-free. But last May, cancer was found in his pelvis and lungs — and he was told he had months, maybe a year, to live.

He wrote the song, “Clouds,” as a farewell. Hallberg said proceeds from the sale of the song, and Sobiech’s other music, are going to the Zach Sobiech Osteosarcoma Fund, which Zach wanted set up so that more research could be done to find better ways to treat this form of childhood cancer.

“That will be Zach’s lasting legacy,” Hallberg said.

Zach’s family members were declining interviews but said in a statement that they felt blessed by Zach’s “amazing presence” in their lives. They thanked those who “listened with their hearts and helped Zach bring his message and his music to the world.”