(CNN) Sen. Bernie Sanders has raised $18.2 million from 525,000 individual donors since entering the Democratic presidential primary in February, his campaign said Tuesday.

One in five of those donors gave to Sanders for the first time, campaign manager Faiz Shakir told reporters. That total, amassed over 41 days culminating with Sunday's quarterly deadline, means Sanders enters the second phase of the campaign with $28 million in cash-on-hand.

Sanders' first quarter haul exceeded that of California Sen. Kamala Harris, who announced about a month earlier; she raised $12 million, her campaign said on Monday night. Pete Buttigieg, the mayor of South Bend, Indiana, took in more than $7 million, according to his team.

Sanders' average donation clocked in at around $20.

The Sanders fundraising numbers confirm his status as a frontrunner in the increasingly crowded race for the Democratic nomination. Former US Rep. Beto O'Rourke has not yet released his figures for the quarter. O'Rourke raised $6.1 million during his first day as a candidate, slightly more than Sanders' $5.9 million. Sanders took in more than half his $18.2 million during the first week of his campaign.

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