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# 91 (number)

 ← 90 91 92 →
Cardinalninety-one
Ordinal91st
(ninety-first)
Factorization7 × 13
Divisors1, 7, 13, 91
Greek numeralϞΑ´
Roman numeralXCI
Binary10110112
Ternary101013
Quaternary11234
Quinary3315
Senary2316
Octal1338
Duodecimal7712
Vigesimal4B20
Base 362J36

91 (ninety-one) is the natural number following 90 and preceding 92.

## In mathematics

91 is:

The decimal equivalent of the fraction ​191 can be obtained by using powers of 9.

## In other fields

Ninety-one is also:

## References

1. ^ "Sloane's A000384 : Hexagonal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-29.
2. ^ "Sloane's A003215 : Hex (or centered hexagonal) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-29.
3. ^ "Sloane's A060544 : Centered 9-gonal (also known as nonagonal or enneagonal) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-29.
4. ^ "Sloane's A005898 : Centered cube numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-29.
5. ^ "Sloane's A000330 : Square pyramidal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-29.
6. ^ Friedman, Erich. What's Special About This Number?