The 25 (number) reference article from the English Wikipedia on 24-Jul-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

25 (number)

25 (twenty-five) is the natural number following 24 and preceding 26.

List of numbers — Integers << 20 21 22 23 24 25 26 27 28 29 >>
Cardinal	twenty-five
Ordinal	twenty-fifth
Factorization
Roman numeral	XXV
Binary	11001
Hexadecimal	19

In mathematics

It is a square number, being 5² = 5 × 5, and it is also the sum of two squares, 3² + 4², often used in demonstrations of the Pythagorean theorem. It is the smallest square that's also a sum of two squares.

It is also a Cullen number. 25 is the smallest pseudoprime satisfying the congruence 7ⁿ = 7 mod n. It is also a Somer pseudoprime based on 6.

Within base 10 one can readily test for divisibility by 25 by seeing if the last two digits of the number match 25, 50, 75 or 00. As a consequence of that, it is a 1-automorphic number.

In other fields

Twenty-five is:

• The atomic number of manganese.
• The number of years of marriage marked in a silver wedding anniversary.
• The minimum age of candidates for election to the United States House of Representatives. "Under 25" provides a common cut-off point for designating youth.
• The number of cents in a quarter, an American coin with George Washington's portrait, and a Canadian coin.
• The designation of United States Interstate 25, a freeway that runs from New Mexico to Wyoming.
• The (critical) number of Florida electoral votes for the 2000 U.S. presidential election.
• Historical years: 25 A.D., 25 B.C, or (for example) 1925

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