### About the Number 691 (six hundred ninety-one)

691 was the MAA (Mathematical Association of America) number of the day on 19 February 2013.

```   MathBabbler Number Analyst (MBNA) output:
=========================================
691 is a natural, whole, integer
691 is odd
691 proper divisors are: 1,
691 is deficient (sum of divisors is 1)
691 is unhappy
691 is a Squarefree Number
691 is not a Harshad number
691 is prime
...Truman Gerald prime with 661
...OEIS:002145 (4n+3; n=164)
691 is the sum of 13 consecutive primes
691 = 29 + 31 + 37 + 41 + 43 + 47 + 53 + 59 + 61 + 67 + 71 + 73 + 79
691 in octal is 01263
691 in hexadecimal is 0x2b3
691 in binary is 1010110011 (is evil)
691 nearest square numbers: -15...38 (676...729 )
sqrt(691) = 26.2869
ln(691) = 6.53814
log(691) = 2.83948
691 reciprocal is .00144717800289435600578871201157
691! is 6.32012e+1663
691 is 219.952 Pi years
691 is 34 score and 11 years
691 written as a Roman numeral is DCXCI
691 = 346^2 - 345^2 and 346 + 345 = 691
```

The MAA reported that `691` is the "only prime number that is a square when turned upside down (169) and another square when reversed (196).

The MBNA reported that `691` is the sum of 13 consecutive primes and the MAA reported that it is the "smallest prime that can be written as the sum of thirteen consecutive primes."

Creator: Gerald Thurman [gthurman@gmail.com]
Created: 19 February 2013 