273 (number)

273 (two hundred [and] seventy-three) is the natural number following 272 and preceding 274.

In mathematics

273 is a sphenic number, being the product of three distinct primes: 3 × 7 × 13. It is also a lucky number, a truncated triangular pyramid number, and an idoneal number.

There are 273 different ternary trees with five nodes. It is in the Moser–de Bruijn sequence, comprising the sum 4⁴ + 4² + 4⁰ = 256 + 16 + 1, and is a central polygonal number.

273 is a deficient number, as the sum of its proper divisors (175) is less than itself.

In science

The number 273 has particular significance in temperature measurement. Absolute zero, the lowest possible temperature, is , often rounded to −273 °C. Correspondingly, the freezing point of water at standard pressure is approximately 273 K (273.15 K exactly).

This relationship arises from Charles's law, which determined that at constant pressure, ideal gases expand or contract their volume by about per degree Celsius of temperature change.

In astronomy

• 273 Atropos is a main-belt asteroid discovered by Austrian astronomer Johann Palisa on 8 March 1888 in Vienna. It is named after Atropos, one of the Three Fates in Greek mythology.
• NGC 273 is an edge-on lenticular galaxy in the constellation Cetus, discovered on 10 September 1785 by William Herschel.

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