### About the Number 91 (ninety-one)

Paul Harvey died at the age of 90. MathBabbler already had a nBAB for the number 90, but he didn't have a nBab for the numbers 89 and `91`. This nBAB is for the number `91`.

```   MathBabbler Number Analyst (MBNA) output:
=========================================
91 is a natural, whole, integer
91 is odd
91 proper divisors are: 1,7,13,
91 is deficient (sum of divisors is 21)
91 is happy
91 is not a Harshad number
91 is not prime
91 is undulating
91 has the prime factors: 7*13
91 is semiprime (biprime or 2-almost prime)
91 in octal is 0133
91 in hexadecimal is 0x5b
91 in binary is 1011011 (is odious)
91 nearest square numbers: -10...9 (81...100 )
sqrt(91) = 9.53939
ln(91) = 4.51086
log(91) = 1.95904
91 reciprocal is .01098901098901098901098901098901
91! is 1.352e+140
91 is 28.9662 Pi years
91 is 4 score and 11 years
91 written as a Roman numeral is XCI
```

This was the `91`st BAB posted during the Spring 2009 BABbling session.

`[Wikipedia]` `91` is the "smallest positive integer expressible as a sum of two cubes in two different ways if negative roots are allowed: `91` = 6^3+(-5)^3 = 4^3+3^3.

MathBabbler needs to look more closely at the McCarthy 91 function.

Creator: Gerald Thurman [gthurman@gmail.com]
Created: 01 March 2009 