Whenever one reports on the "oldest," the "youngest," the "longest," the "most" or the "least" of anything, one must be prepared to be challenged. So it was the other day when reader Steve Bienstock suggested that the late Rep. Emanuel Celler of New York, the longtime chairman of the House Judiciary Committee, might belong on the list of the oldest active former members of Congress.

Our published list, provided by L. Robert Davids, was of 14 who reached the age of 86 while serving on the Hill.

Sorry, Mr. Bienstock, but Manny Celler didn't make it. He was a youthful 85 years and 4 months when he decided to go back to Brooklyn. But he did rack up the second highest seniority on record in the House of Representatives, 49 years 10 months and 13 days.

The all-time record for congressional service was held by Carl Hayden of Arizona, who served 56 years 10 months and 28 days in the House and Senate, 41 of those years in the Senate where he also served longer than anybody. He entered Congress in 1912 when Arizona entered the union.

Washingtonians of today's adult generation will recognize four who are in the top five of all-time House seniority and four of the five with comparable Senate longevity. The lists:

Rep. Carl Vinson of Georgia, 50 years 2 months and 13 days; Celler, 49-10-13; Sam Rayburn of Texas, the longtime speaker, 48-8-25; Wright Patman, also of Texas, 47-0-25, and Joseph Cannon of Illinois, whose interrupted terms spanned 1873 to 1923, 46-0-11.

Senate records don't break it down so fine, so we find Hayden with 41 years, Richard Russell of Georgia with 38 years and incumbent John Stennis of Mississippi closing in fast (he'll overtake Russell on Nov. 15). Francis E. Warren of Wyoming (Gen. John J. Pershing's father-in-law) had 37 years and James Eastland of Missisippi served 36 years.