New York Gov. Andrew Cuomo has $23.7 million in cash on hand. Associated Press

New York Gov. Andrew Cuomo wields an enormous financial advantage over his GOP challenger, Rob Astorino, with about a month to go before the Nov. 4 election, according to their campaign-finance filings on Friday.

Mr. Cuomo, a Democrat, has $23.7 million in cash on hand, according to documents filed with the state Board of Elections, after having spent about $3.3 million and raised $561,371 since the last filings two weeks ago.

By contrast, Mr. Astorino, the Westchester county executive, has nearly $1.3 million in cash on hand—about 5% of Mr. Cuomo’s haul. Mr. Astorino’s campaign raised about $1.5 million since its last filing, in July, and spent $2.6 million during that period.

Mr. Astorino’s largest individual donors were billionaire hedge-fund manager John Paulson and his wife, Jenica, who combined gave more than $82,000. The maximum contribution per election cycle to a gubernatorial candidate in New York state is $60,800 per individual.

A spokesman for Mr. Paulson declined to comment on the couple’s support of Mr. Astorino.

The vast majority of Mr. Astorino’s donors, however, contributed less than $1,000 apiece.

A spokeswoman for Mr. Astorino, Jessica Proud, said that the campaign is a “grassroots movement,” adding that “we are enormously proud that we have reached over 7,000 individual donors.”

“In Cuomo’s New York only the wealthy, well-connected few get ahead,” she said. “Even with all his pay-to-play millions and taxpayer funded ads, the majority of New Yorkers still think he’s doing a poor job.”

A spokesman for Mr. Cuomo declined to comment.

The filings came on the cusp of an active weekend for both campaigns. On Saturday, Mr. Cuomo plans to board a bus, which he has dubbed the “Women’s Equality Express,” to tour a trio of upstate cities—Albany, Syracuse and Rochester—in support of a slate of gender-equity legislation that has become a centerpiece of his campaign.

After Mr. Cuomo announced his bus tour, Mr. Astorino’s campaign said it would trail the governor’s vehicle in a van dubbed the “Shelly Silver Express,” designed to draw attention to Mr. Cuomo’s reluctance to involve himself in several episodes involving state Assembly Speaker Sheldon Silver.

In May of last year, Mr. Silver was identified in an ethics report as a pivotal figure in a decision to conceal sexual-harassment allegations against a member of his conference.

At the time, Mr. Silver acknowledged having made mistakes. While Mr. Cuomo was critical of the matter, he didn’t call for Mr. Silver to resign from the speakership.

A spokesman for Mr. Silver said it is “inappropriate to attack” the speaker, an observant Jew, on Yom Kippur.

Meanwhile, should Mr. Cuomo be inclined to disembark from his bus at the Syracuse stop, Green Party gubernatorial candidate Howie Hawkins has offered to give the governor a pedicab tour of his Syracuse neighborhood on Saturday in an effort to demonstrate how he believes Mr. Cuomo’s economic policies exacerbate income inequality.

Write to Erica Orden at erica.orden@wsj.com