“All my generation knows nothing about the Holocaust,” said Ms. Sagir, 21, who has had the tattoo for four years. “You talk with people and they think it’s like the Exodus from Egypt, ancient history. I decided to do it to remind my generation: I want to tell them my grandfather’s story and the Holocaust story.”

Mr. Diamant’s descendants are among a handful of children and grandchildren of Auschwitz survivors here who have taken the step of memorializing the darkest days of history on their own bodies. With the number of survivors here dropping to about 200,000 from 400,000 a decade ago, institutions and individuals are grappling with how best to remember the Holocaust — so integral to Israel’s founding and identity — after those who lived it are gone.

Rite-of-passage trips to the death camps, like the one Ms. Sagir took, are now standard for high school students. The Holocaust memorial Yad Vashem in Jerusalem and other museums are trying to make exhibits more accessible, using individual stories and special effects. Arguments rage about whether that approach trivializes symbols long held as sacred and whether the primary message should be about the importance of a self-reliant Jewish state in preventing a future genocide or a more universal one about racism and tolerance.

“We are moving from lived memory to historical memory,” noted Michael Berenbaum, a professor at the American Jewish University in Los Angeles who is among the foremost scholars of the memorialization of the Holocaust. “We’re at that transition, and this is sort of a brazen, in-your-face way of bridging it.”

Mr. Berenbaum said that “replicating an act that destroyed their name and made them into a number would not be my first or second or third choice,” but, he added, “it sure beats some of the other tattoos that some of the young people are drawing on their skin.”

It is certainly an intensely personal decision that often provokes ugly interactions with strangers offended by the reappropriation of perhaps the most profound symbol of the Holocaust’s dehumanization of its victims. The fact that tattooing is prohibited by Jewish law — some survivors long feared, incorrectly, that their numbers would bar them from being buried in Jewish cemeteries — makes the phenomenon more unsettling to some, which may be part of the point.

“It’s shocking when you see the number on a very young girl’s hand,” Ms. Sagir said. “It’s very shocking. You have to ask, Why?”

Tattooing was introduced at Auschwitz in the autumn of 1941, according to the United States Holocaust Memorial Museum’s Encyclopedia of the Holocaust, and at the adjacent Birkenau the next March. They were the only camps to employ the practice, and it is unclear how many people were branded, briefly on the chest and more commonly on the left forearm.

Only those deemed fit for work were tattooed, so despite the degradation, the numbers were in some cases worn with pride, particularly lower ones, which indicated having survived several brutal winters in the camp. “Everyone will treat with respect the numbers from 30,000 to 80,000,” Primo Levi wrote in his seminal memoir, “Survival in Auschwitz,” describing the tattoos as part of “the demolition of a man.”

After the war, some Auschwitz survivors rushed to remove the tattoos through surgery or hid them under long sleeves. But over the decades, others played their numbers in the lottery or used them as passwords.

Dana Doron, a 31-year-old doctor and daughter of a survivor, interviewed about 50 tattooed survivors for the new Israeli documentary “Numbered,” which she directed with Uriel Sinai, a photojournalist; it will make its premiere in the United States next month at the Chicago International Film Festival.

When she asked survivors whether lovers kissed the number as they might a scar, Ms. Doron said, “some of them looked at me like, ‘What are you nuts?’ and some of them said, ‘Of course.’ ”

“To me, it’s a scar,” said Ms. Doron, who grew interested in the numbering while drawing blood from a tattooed arm in an emergency room. “The fact that young people are choosing to get the tattoos is, in my eyes, a sign that we’re still carrying the scar of the Holocaust.”

“Numbered” follows Hanna Rabinovitz, a middle-aged woman who puts her father’s number on her ankle after his death. The film also tells the story of Ayal Gelles, a 28-year-old computer programmer, and his grandfather, Avraham Nachshon, 86, both of whom bear the number A-15510 on their arms.

“Like an inheritance or something,” Mr. Gelles said of his tattoo. “It’s provocative, I guess. Everyone is kind of appalled at first, kind of shocked by it.”

Mr. Gelles said he had an epiphany seeing cows branded at a ranch in Argentina, leading him to get the tattoo and to adopt a vegan diet. He did not tell Mr. Nachshon of his plan.

“If I knew, I would have said to you not to do it,” the grandfather told his grandson one recent evening.

“I dream every night about it,” Mr. Nachshon said as he told his Holocaust story, which includes several months at Birkenau, where his mother and sister were killed in the gas chambers. “Many times we’re running away from the Germans. Sometimes the whole night I was running. Maybe this time they won’t catch me.”

Mr. Nachshon swims, does yoga or runs on a treadmill each morning, returning home by 2 p.m. to feed the neighborhood cats and pass the hours in front of the TV. A couple of times a week, Mr. Gelles comes for supper at his Tel Aviv apartment, and they watch TV together.

“Every time I see it, it’s a reminder to call him,” Mr. Gelles said of the number. “I find it kind of hard to relate to people I don’t know and places I haven’t been to and this thing called the Holocaust. The thing I relate to more is my grandfather.”

The Israeli who tattooed Livia Ravek’s number, 4559, on her son, Oded Ravek, and grandson, Daniel Philosoph, did it free.

It was a Friday. Mr. Ravek, a 56-year-old glass artist who lives in Ottawa and was here visiting family when he was tattooed two years ago, brought Sabbath flowers to his mother. “She was really upset about it at first,” he said. “When I explained the reasons for why I did it, we cried together. I said, ‘You’re always with me.’ ”

The 10 tattooed descendants interviewed for this article echoed one another’s motivations: they wanted to be intimately, eternally bonded to their survivor-relative. And they wanted to live the mantra “Never forget” with something that would constantly provoke questions and conversation.

Ms. Sagir, a cashier at a minimarket in the heart of touristy Jerusalem, said she is asked about the number 10 times a day. There was one man who called her “pathetic,” saying of her grandfather, “You’re trying to be him and take his suffering.” And there was a police officer who said, “God creates the forgetfulness so we can forget,” Ms. Sagir recalled. “I told her, ‘Because of people like you who want to forget this, we will have it again.’ ”

One recent Friday, Ms. Sagir accompanied her uncle, Doron Diamant, 40, a carpenter and father of four, to the tattoo parlor. He was the fifth descendant of Yosef Diamant — who died last year at 84 — to be tattooed.

It was done in 15 minutes, for about $40. When the tattoo artist, a Russian immigrant, joked that he is “not so patriotic” to do it at a discount, Mr. Diamant quietly seethed.

“This is the reason he sits here, this tattoo and what this number represents,” Mr. Diamant said. “We got the country because of these people.”