91 (ninety-one) is a positive integer following 90 and preceding 92. Its ordinal form is written "ninety-first" or 91st.


91 is an odd composite number[1].

91 is the 13th triangular number, and therefore the number of tiles in a double-12 domino set.

In googology

In Greek-based number-naming systems, 91 is associated with prefix "henenneaconta-", and with prefix "unnonaginti-" in Latin systems.


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


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