### About the Number 78 (seventy-eight)

MathBabbler created a nBAB for the number 77 on 29 March 2009. While working on that nBAB, he learned that 77 was a Ruth-Aaron pair with `78`. On 31 March 2009, MathBabbler and his CSC100 class wrote a C program that determines if a number is a member of the Ruth-Aaron pair. This nBAB about the number `78` is the first nBAB to use the MBNA's Ruth-Aaron program.

```   MathBabbler Number Analyst (MBNA) output:
=========================================
78 is a natural, whole, integer
78 is even
78 proper divisors are: 1,2,3,6,13,26,39,
78 is abundant (sum of divisors is 90)
78 is unhappy
78 is not a Harshad number
78 is not prime
78 has the prime factors: 2*3*13
78 is sphenic (had 3 unique prime factors)
78 sum prime factors: 2...3...13...answer: 18
78 is undulating
78 and 77 are a Ruth-Aaron pair
78 and 77 are a Ruth-Aaron pair (distinct prime factors)
78 in octal is 0116
78 in binary is 1001110 (is evil)
78 nearest square numbers: -14...3 (64...81 [9])
sqrt(78) = 8.83176
ln(78) = 4.35671
log(78) = 1.89209
78 reciprocal is .01282051282051282051282051282051
78! is 1.13243e+115
78 is 24.8282 Pi years
78 is 3 score and 18 years
78 written as a Roman numeral is LXXVIII
```

`[Wikipedia]` `78` is a triangular number. A triangular number is the "number of dots in an equilateral triangle evenly filled with dots. For example, three dots can be arranged in a triangle; thus three is a triangle number."

On 2 April 2009, when this nBAB was created, the MBNA was not checking from triangular numbers.

OEIS.org::id:A000217

##### Update::2009.10.04

Pavel Popovich, the 6th man to orbit Earth, died on 29 September 2009 at the age of `78`.

`log4(78)` approximates Pi rounded to the nearest hundredth.

`7813` equals repdigit number 99.

BAB created on 4 October 2009... BAB::Pavel Popovich is Dead at 78

Creator: Gerald Thurman [gthurman@gmail.com]
Created: 02 April 2009