President Barack Obama visits Hiroshima on Friday, the first sitting American president to do so since the U.S. dropped an atomic bomb on the city in western Japan on Aug. 6, 1945. A second atomic bomb was dropped on Nagasaki three days later. The U.S. has said the bombings hastened Japan's surrender and eliminated the need for a U.S. invasion that would have cost many more lives. The toll on the two Japanese cities was heavy. Here's a look, by the numbers, at the atomic bombing of Hiroshima:

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350,000: Population of Hiroshima before the bombing, of which 40,000 were military personnel.

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140,000: Estimated death toll, including those who died from radiation-related injuries and illness through Dec. 31, 1945.

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300,000: Total death toll to date, including those who have died from radiation-related cancers.

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1.2 million: Population of Hiroshima today.

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31,500: Height in feet (9,600 meters) from which the B-29 Enola Gay dropped the "Little Boy" bomb.

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2,000: Height in feet (600 meters) at which the bomb exploded 43 seconds after it was dropped.

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3,000-4,000: The estimated temperature in Celsius (5,400-7,200 Fahrenheit) at ground zero seconds after the detonation.

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8,900: Approximate weight of the "Little Boy" bomb in pounds (about 4 metric tons).

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1,600: Radius in feet (500 meters) from ground zero in which the entire population died that day.

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90: Percent of Hiroshima that was destroyed.

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45: Minutes after the 8:15 a.m. blast that a "black rain" of highly radioactive particles started falling.

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3-6: Weeks after the bombing during which most of the victims with severe radiation symptoms died.

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10 million: Folded paper ("origami") cranes that decorate the Children's Peace Monument in Hiroshima each year.

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Sources: Hiroshima city government; Japan Ministry of Health, Labor and Welfare; Japan Foreign Ministry.