What's a trillion? Not much to Apple CEO Tim Cook.

After Apple (AAPL) became the first American company to hit $1 trillion in market value, Cook sent a letter to his 123,000 employees. He congratulated them, but he told his employees not to let the record-breaking stat distract them from their mission.

"While we have much to be proud of in this achievement, it's not the most important measure of our success," Cook wrote. An Apple spokesman confirmed the letter.

Cook emphasized the company's innovation and principles make Apple one of the world's most valuable businesses.

"It's you, our team, that makes Apple great and our success is due to your hard work, dedication and passion," Cook wrote. "I am deeply humbled by what you do, and it's the privilege of a lifetime to work alongside you."

Apple's CEO said he thanked his staff "from the bottom of my heart" for working late hours, extra trips and "all the times you refuse to settle for anything less than excellence."

Related: Apple reaches $1,000,000,000,000 value

Cook's ambivalence to the $1 trillion mark mirrors what he told CNN's Laurie Segall in June. He said he doesn't think about the valuation.

In the letter, Cook also credited Apple cofounder Steve Jobs for reversing the company's misfortunes.

"Steve founded Apple on the belief that the power of human creativity can solve even the biggest challenges — and that the people who are crazy enough to think they can change the world are the ones who do," Cook wrote.

He ended the letter writing: "Just as Steve always did in moments like this, we should all look forward to Apple's bright future and the great work we'll do together."