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

It is a square number, being 5² = 5 × 5. It is the smallest square that is also a sum of two (non-zero) squares: 25 = 3² + 4². Hence it often appears in illustrations of the Pythagorean theorem.

25 is a centered octagonal number, a centered square number, and an automorphic number.

25 percent is equal to 1/4.

25 has an aliquot sum of 6 and number 6 is the first (or smallest) number to have an aliquot sequence that does not culminate in 0 through a prime. Twenty-five is the aliquot sum of three integers; 95, 119, and 143. Twenty-five is the second composite member of the 6-aliquot tree.

It is the smallest base 10 Friedman number as it can be expressed by its own numbers: 5².

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

25 is the smallest aspiring number — a composite non-sociable number whose aliquot sequence does not terminate.

According to the Shapiro inequality, 25 is the least odd integer n such that there exist Failed to parse (Missing texvc executable; please see math/README to configure.): x_1, x_2, \dots, x_n

A number is a mathematical object used to count and measure. In mathematics, the definition of number has been extended over the years to include such numbers as zero, negative numbers, rational numbers, irrational numbers, and complex numbers.

Mathematical operations are certain procedures that take one or more numbers as input and produce a number as output. Unary operations take a single input number and produce a single output number. For example, the successor operation adds one to an integer, thus the successor of 4 is 5. Binary operations take two input numbers and produce a single output number. Examples of binary operations include addition, subtraction, multiplication, division, and exponentiation. The study of numerical operations is called arithmetic.

A notational symbol that represents a number is called a numeral. In addition to their use in counting and measuring, numerals are often used for labels (telephone numbers), for ordering (serial numbers), and for codes (e.g., ISBNs).

Neil Percival Young,OC,OM (born November 12, 1945) is a Canadian singer-songwriter who is widely regarded as one of the most influential musicians of his generation.

Young began performing as a solo artist in Canada in 1960, before moving to California in 1966, where he co-founded the band Buffalo Springfield along with Stephen Stills and Richie Furay, and later joined Crosby, Stills & Nash as a fourth member in 1969. He forged a successful and acclaimed solo career, releasing his first album in 1968; his career has since spanned over 40 years and 34 studio albums, with a continual and uncompromising exploration of musical styles. The Rock and Roll Hall of Fame website describes Young as "one of rock and roll’s greatest songwriters and performers". He has been inducted into the Hall of Fame twice: first as a solo artist in 1995, and second as a member of Buffalo Springfield in 1997.

Young's work is characterized by his distinctive guitar work, deeply personal lyrics and signature alto or high tenor singing voice. Although he accompanies himself on several different instruments, including piano and harmonica, his idiosyncratic electric and clawhammer acoustic guitar playing are the defining characteristics of a varyingly ragged and melodic sound. While Young has experimented with differing music styles, including swing and electronic music throughout a varied career, his best known work usually falls into two primary styles: acoustic (folk and country rock) and electric (amplified hard rock, very often in collaboration with the band Crazy Horse). Young has also adopted elements from newer styles such as alternative rock and grunge. His influence on the latter caused some to dub him the "Godfather of Grunge".

Wolfgang Amadeus Mozart (German: [ˈvɔlfɡaŋ amaˈdeus ˈmoːtsaʁt], English see fn.), baptismal name Johannes Chrysostomus Wolfgangus Theophilus Mozart (27 January 1756 – 5 December 1791), was a prolific and influential composer of the Classical era. He composed over 600 works, many acknowledged as pinnacles of symphonic, concertante, chamber, operatic, and choral music. He is among the most enduringly popular of classical composers.

Mozart showed prodigious ability from his earliest childhood in Salzburg. Already competent on keyboard and violin, he composed from the age of five and performed before European royalty. At 17, he was engaged as a court musician in Salzburg, but grew restless and travelled in search of a better position, always composing abundantly. While visiting Vienna in 1781, he was dismissed from his Salzburg position. He chose to stay in the capital, where he achieved fame but little financial security. During his final years in Vienna, he composed many of his best-known symphonies, concertos, and operas, and portions of the Requiem, which was largely unfinished at the time of his death. The circumstances of his early death have been much mythologized. He was survived by his wife Constanze and two sons.