About the Number 991 (nine hundred ninety-one)

`@MathBabbler` received the following tweet from `@MAAnow` on `2010.03.01`.

```   Today's Number: 991 http://cot.ag/9bnoi7
```
```   MathBabbler Number Analyst (MBNA) output:
=========================================
991 is a natural, whole, integer
991 is odd
991 proper divisors are: 1,
991 is deficient (sum of divisors is 1)
991 is unhappy
991 is not a Harshad number
991 is prime
...Sexy prime with 997
...OEIS:002145 (4n+3; n=247)
...Super
991 is a lucky number
991 is the sum of 7 consecutive primes
991 = 127 + 131 + 137 + 139 + 149 + 151 + 157
991 in octal is 01737
991 in binary is 1111011111 (is odious)
991 nearest square numbers: -30...33 (961...1024 [32])
sqrt(991) = 31.4802
ln(991) = 6.89871
log(991) = 2.99607
991 reciprocal is .00100908173562058526740665993945
991! is 4.1718e+2540
991 is 315.445 Pi years
991 is 49 score and 11 years
991 written as a Roman numeral is CMXCI
991 = 496^2 - 495^2 and 496 + 495 = 991
```

The MAA's NumberADay indicated that `991` is the "largest three-digit permutable prime. In other words, 991, 919, and 199 are all primes."

Creator: Gerald Thurman [gthurman@gmail.com]
Created: 01 March 2010