231 (number)

231 (two hundred [and] thirty-one) is the natural number following 230 and preceding 232.

In mathematics

Two hundred [and] thirty-one 231 = 3·7·11, sphenic number, triangular number, hexagonal number, octahedral number, centered octahedral number, the number of integer partitions of 16, Mertens function returns 0, and is the number of cubic inches in a U.S. liquid gallon.

In chemistry

• Ac-231 is an isotope of actinium.
• Am-231 is an artificial isotope of americium.
• Pa-231 is a naturally occurring isotope of protactinium.
• Ra-231 is an isotope of radium.
• Th-231 is an isotope of thorium.

In other fields

231 is:

• The year A.D. 231 or 231 BC.
• +231 is the country code for Liberia.
• Pacific 231, an orchestral work by French composer Arthur Honegger.
• Pacific 231, a 1949 short film directed by Jean Mitry.
• M-231 (Michigan highway), a highway in Michigan