SEC Form 424B3 filed by National Rural Utilities Cooperative Finance Corporation
$NRUC
Diversified Financial Services
Finance
| Filed under Rule 424(b)(3), Registration Statement No. 333-275151 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Pricing Supplement No. 644 - Dated Monday, August 25, 2025 (To: Prospectus Dated October 24, 2023 and Prospectus Supplement Dated October 27, 2023) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| CUSIP Number | Principal Amount | Selling Price | Gross Concession | Net Proceeds | Coupon Type | Coupon Rate | Coupon Frequency | Maturity Date | 1st Coupon Date | 1st Coupon Amount | Survivor's Option | Product Ranking | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 63743F3V6 | [ ] | 100.000% | 0.550% | [ ] | Fixed | 3.850% | Monthly | 09/15/2027 | 10/15/2025 | $4.28 | Yes | Senior Unsecured Notes | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Redemption Information: Non-Callable
| Offering Date: Monday, August 25, 2025 through Tuesday, September 2, 2025 | National Rural Utilities Cooperative Finance Corp | |||||||
| National Rural Utilities Cooperative Finance Corp | Trade Date: Tuesday, September 2, 2025 @12:00 PM ET | |||||||
| Settle Date: Friday, September 5, 2025 | Prospectus dated October 24, 2023 and | |||||||
| Minimum Denomination/Increments:$1,000.00/$1,000.00 | Prospectus Supplement Dated: October 27, 2023 | |||||||
| Initial trades settle flat and clear SDFS: DTC Book Entry only | ||||||||
| DTC Number: 0235 via RBC Dain Rauscher Inc. | ||||||||
| Agents: InspereX LLC, Citigroup Global Markets Inc., Wells Fargo Clearing Services, LLC, RBC Capital Markets, LLC | ||||||||
| Trustee: U.S. Bank Trust Company, National Association | ||||||||
| If the maturity date or an interest payment date for any note is not a business day (as term is defined in prospectus), principal, premium, if any, and interest for that note is paid on the next business day, and no interest will accrue from, and after, the maturity date or interest payment date. | ||||||||
| Notes will be sold to you at the selling price specified in this Pricing Supplement. The Purchasing Agent shall purchase notes from us at the selling price less the applicable gross concession specified in this Pricing Supplement. The Purchasing Agent may resell the notes it purchases to the agents and selected dealers at the selling price less a concession that, at the discretion of the Purchasing Agent, may be less than or equal to the gross concession received by the Purchasing Agent. Notes purchased by the agents and selected dealers on behalf of level-fee [investment or advisory] accounts may be sold to such accounts at the selling price less the applicable concession, and such agents and selected dealers shall not retain, as compensation, any portion of such concession. | ||||||||
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