63

63 is a natural number that follows 62 and precedes 64. It is an odd composite number with prime factorization 3^2 × 7.

Divisors of 63 are 1, 3, 7, 9, 21, and 63. In binary it is 111111, and it equals 2^6 − 1, highlighting its relation to powers of two. It has several common base representations: decimal 63, hexadecimal 3F, octal 77, and other bases such as 333_4, 2100_3, 143_6, 120_7, 77_8, 70_9, and 223_5.

In science and technology, 63 is the atomic number of Europium, a lanthanide metal used in phosphors for red displays and in some neutron-absorbing materials for nuclear reactors.

In astronomy, Messier 63, the Sunflower Galaxy, is a spiral galaxy in Canes Venatici, discovered by Pierre Méchain in 1779.

Geographically and culturally, the 63rd parallel north is a circle of latitude that crosses parts of North America and Europe. In Roman numerals, 63 is written LXIII.