90 (ninety) is a positive integer following 89 and preceding 91. Its ordinal form is written "ninetieth" or 90th.


90 is an even composite number[1].

It is also the number of primordial nuclides without energetically allowed baryon number-preserving decay modes.

90 is the third unitary perfect number.

In googology

In Greek-based number-naming systems, 90 is associated with prefix "enneaconta-", and with prefix "nonaginti-" in Latin systems.

As a banknote denomination

The third Burmese kyat had banknotes with this number in the denomination.

In Germany

It is an abbreviation for the year, in which the Nationalelf won its third FIFA World Cup title.

For this reason, it has been used in a song by the Sportfreunde Stiller.

In the same year, the German reunification took place. For this reason, it has been used in the name of a political party.


  1. OEIS, Sequence A002808 (accessed 2021-02-07)


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