Please answer a question about the following table 

header: President | Became Oldest Living President | Ceased to Be Oldest Living President | Age at Start Date | Age at End Date | Duration (Years, Days) | Duration (Days) row 1 : George Washington | April 30, 1789 | December 14, 1799 | 57 years, 67 days | 67 years, 295 days | 10 years, 228 days | 3,880 days
row 2 : John Adams | December 14, 1799 | July 4, 1826 | 64 years, 45 days | 90 years, 247 days | 26 years, 202 days | 9,698 days
row 3 : James Madison | July 4, 1826 | June 28, 1836 | 75 years, 110 days | 85 years, 104 days | 9 years, 360 days | 3,647 days
row 4 : Andrew Jackson | June 28, 1836 | June 8, 1845 | 69 years, 105 days | 78 years, 85 days | 8 years, 345 days | 3,267 days
row 5 : John Quincy Adams | June 8, 1845 | February 23, 1848 | 77 years, 332 days | 80 years, 227 days | 2 years, 260 days | 990 days
row 6 : Martin Van Buren | February 23, 1848 | July 24, 1862 | 65 years, 80 days | 79 years, 231 days | 14 years, 151 days | 5,265 days
row 7 : James Buchanan | July 24, 1862 | June 1, 1868 | 71 years, 92 days | 77 years, 39 days | 5 years, 313 days | 2,139 days
row 8 : Millard Fillmore | June 1, 1868 | March 8, 1874 | 68 years, 146 days | 74 years, 60 days | 5 years, 280 days | 2,106 days
row 9 : Andrew Johnson | March 8, 1874 | July 31, 1875 | 65 years, 69 days | 66 years, 214 days | 1 year, 145 days | 510 days
row 10 : Ulysses S. Grant | July 31, 1875 | July 23, 1885 | 53 years, 95 days | 63 years, 87 days | 9 years, 357 days | 3,645 days
row 11 : Rutherford B. Hayes | July 23, 1885 | January 17, 1893 | 62 years, 292 days | 70 years, 105 days | 7 years, 178 days | 2,735 days
row 12 : Benjamin Harrison | January 17, 1893 | March 13, 1901 | 59 years, 150 days | 67 years, 205 days | 8 years, 55 days | 2,976 days
row 13 : Grover Cleveland | March 13, 1901 | June 24, 1908 | 63 years, 360 days | 71 years, 98 days | 7 years, 103 days | 2,660 days
row 14 : Theodore Roosevelt | June 24, 1908 | March 4, 1909 | 49 years, 241 days | 50 years, 128 days | 0 years, 253 days | 253 days
row 15 : William Howard Taft | March 4, 1909 | March 4, 1913 | 51 years, 170 days | 55 years, 170 days | 4 years, 0 days | 1,461 days
row 16 : Woodrow Wilson | March 4, 1913 | February 3, 1924 | 56 years, 66 days | 67 years, 37 days | 10 years, 336 days | 3,988 days
row 17 : William Howard Taft | February 3, 1924 | March 8, 1930 | 66 years, 141 days | 72 years, 174 days | 6 years, 33 days | 2,225 days
row 18 : Calvin Coolidge | March 8, 1930 | January 5, 1933 | 57 years, 247 days | 60 years, 185 days | 2 years, 303 days | 1,034 days
row 19 : Herbert Hoover | January 5, 1933 | October 20, 1964 | 58 years, 148 days | 90 years, 71 days | 31 years, 289 days | 11,611 days
row 20 : Harry S. Truman | October 20, 1964 | December 26, 1972 | 80 years, 165 days | 88 years, 232 days | 8 years, 67 days | 2,989 days
row 21 : Lyndon B. Johnson | December 26, 1972 | January 22, 1973 | 64 years, 121 days | 64 years, 148 days | 0 years, 27 days | 27 days
row 22 : Richard Nixon | January 22, 1973 | January 20, 1981 | 60 years, 13 days | 68 years, 11 days | 7 years, 364 days | 2,920 days
row 23 : Ronald Reagan | January 20, 1981 | June 5, 2004 | 69 years, 349 days | 93 years, 120 days | 23 years, 137 days | 8,537 days
row 24 : Gerald Ford | June 5, 2004 | December 26, 2006 | 90 years, 327 days | 93 years, 165 days | 2 years, 204 days | 934 days
row 25 : George H. W. Bush | December 26, 2006 | Current oldest living president | 82 years, 197 days | Current oldest living president | 7 years, 173 days | 2,730 days
row 26 : President | Became Oldest Living President | Ceased to Be Oldest Living President | Age at Start Date | Age at End Date | Duration (Years, Days) | Duration (Days)

which u.s. presidents have ever held the title oldest living president? of these presidents, which ones held the title for over 20 years?

Answer: John Adams, Herbert Hoover, Ronald Reagan