2645

2645 is a natural number that follows 2644 and precedes 2646. It is an odd composite number with prime factorization 5 × 23^2 (that is, five times twenty-three squared). The divisors of 2645 are 1, 5, 23, 115, 529, and 2645.

Its sum of divisors is 3318, making the sum of proper divisors 673. Consequently, 2645 is a deficient number. In various numeral systems, 2645 is written in binary as 101001010101 and in hexadecimal as 0xA55. In Roman numerals it is MMDCXLV.

2645 is also the numerical designation of a minor planet in the catalog of the Minor Planet Center.

As a year, 2645 CE would fall in the 27th century; if used in historical fiction or futures contexts it would be a distant, speculative date.