The historian and social critic Ibram X. Kendi is used to getting hate mail. And sometimes the disdain for him and his work takes the form of a phone call. So when he does not recognize the number he does not often answer.

Such was the case on a recent day when Dr. Kendi, who wrote the best-selling book, “How to Be an Antiracist,” ignored a call from Chicago. It would take a text-message exchange with the caller and a little online sleuthing, but he eventually discovered that the person calling was from the John D. and Catherine T. MacArthur Foundation. He was intrigued: Were they calling to talk about a potential research collaboration — or was it something else?

Dr. Kendi let them call again. And when he picked up, he would learn that the foundation was calling to convey happy news — the something else he had allowed as a possibility: He had been awarded a prestigious (and lucrative) MacArthur Fellowship.

“My first words were ‘Are you serious?’” he recalled. Indeed, they were.

“It’s very meaningful — I think to anyone who studies a topic where there’s a lot of acrimony and a lot of pain — to be recognized and to get love mail sometimes,” he said. “And this is one of the greatest forms of that I have ever received.”

Dr. Kendi, 39, is perhaps the most widely known of the 25 people in this year’s class of MacArthur Fellows. His 2019 book, “How to Be an Antiracist,” has sold two million copies and established him as one of the country’s leading commentators on race since the George Floyd protests last year.

But the MacArthur Fellowship is not simply love mail. It comes with a no-strings-attached grant of $625,000, to be awarded over five years. And it is known colloquially as the “genius” award, to the sometime annoyance of the foundation.

Cecilia Conrad, managing director of the program, said the goal of the awards is to recognize “exceptional creativity,” as well as future potential, across the arts, sciences, humanities, advocacy and other fields.

“We want to have a share in people who are at a pivotal moment, when the fellowship could accelerate what their future could look like,” she said.

Most of the 2021 fellows, while esteemed in their fields, have yet to become household names.

There are artists and writers like the poet and lawyer Reginald Dwayne Betts, the critic, essayist and poet Hanif Abdurraqib; the novelist and radio producer Daniel Alarcón; and the writer and curator Nicole R. Fleetwood, whose book “Marking Time: Art in the Age of Mass Incarceration” won the 2021 National Book Critics Circle Award for criticism.

Dr. Fleetwood, 48, who is also a professor of media, culture and communication at New York University, curated an exhibition by the same name that won praise after its debut at MoMA PS1 last year. In the book and the accompanying museum exhibition, Dr. Fleetwood delves into the cultural and aesthetic significance of the art made by incarcerated people.

“To me, one of the great gifts for people who go to the show or read the book is that it challenges their assumptions about who’s incarcerated, why they are incarcerated and what they do with their time,” Dr. Fleetwood said.

The grant will help the “Marking Time” project expand its footprint on tour, she added, noting that she had recently helped install the exhibition in Birmingham. Ala.

Other fellows in this year’s class include Trevor Bedford, a virologist who is developing real-time tools for tracking virus evolution; Marcella Alsan, a physician and economist who studies how the legacies of discrimination perpetuate health inequalities; and Desmond Meade, a civil rights activist who works to restore voting rights to formerly incarcerated people.

And there are several fellows who work with or study technology. Joshua Miele, a technology designer at Amazon, develops devices that help visually impaired or blind people like himself gain access everyday to tech products and digital information. Safiya Noble, a digital media scholar, has written about how search engines reinforce racist and sexist stereotypes.

The youngest fellow is Jordan Casteel, 32, a painter known for portraits that capture everyday encounters with people of color. The oldest is Jawole Willa Jo Zollar, 70, a choreographer who founded the performance ensemble Urban Bush Women.

Unusually, the fellows include a married couple, Cristina Ibarra, a documentary filmmaker who chronicles border communities, and Alex Rivera, a filmmaker who explores issues around migration to the United States. The couple, who sometimes collaborate, were evaluated and selected separately, but informed together.

“It was a lot of fun to call them,” Ms. Conrad said.

Few honors carry the prestige — and mystique — of the MacArthurs. Potential fellows cannot apply but are suggested by a network of hundreds of anonymous nominators from across the country and narrowed down by a committee of about a dozen people, whose names are not released.

“There is nothing like being recognized by your peers,” Dr. Kendi said. “We’re all creating, writing and functioning in communities. We as individuals are nothing without the communities where we create and work.”

There is no theme to any given class, Ms. Conrad said. But virtually all this year’s winners outside the sciences do work relating to social and racial justice. And that meshes with the funding priorities of the foundation, which was one of five foundations that last June pledged additional payouts of $1.7 billion in response to the pandemic, in part financed by issuing debt.

In July, the foundation, whose endowment in December 2020 was $8.2 billion, announced $80 million in grants to support “an equitable recovery from the pandemic and combat anti-Blackness, uplift Indigenous Peoples and improve public health equity.”

Another fellow, Monica Muñoz Martinez, a historian at the University of Texas, Austin, is a co-founder of Refusing to Forget, a nonprofit that promotes awareness of the largely ignored history of racial violence along the U.S.-Mexico border in the early 20th century, which she recounted in her 2018 book “The Injustice Never Leaves You: Anti-Mexican Violence in Texas.”

It’s a hotly contested subject in Texas, which has been flooded by legislation that seeks to play down references to slavery and anti-Mexican discrimination in the teaching of state history.

“As a historian who studies histories of racist violence, and who studies the long struggle for civil rights and for social justice, it is unsettling every day to see so many of the dangerous patterns from the past repeating,” Dr. Martinez said.

“We are living in a moment where there are organized efforts to restrict rights: Voting rights, reproductive rights, you could talk about immigration all afternoon,” she added. “There is so much at stake.”