About the Number 70 (seventy)

MathBabbler posted a nBAB for the number 31 and he noticed he didn't have a nBAB for the number 30. He did have nBABs for 10, 20, 40, 50, 60, 90, 100, 200, 500, 1500, 1600, 1700, 1800, 1900, 2000, 2100 and 8100 (all multiples of 10). MathBabbler opted to create a nBAB for the number 80 because his mom turned 80 in 2009. After posting the nBAB for the number 80 he decided to go ahead and create a nBAB for the number 30. Given he had nBABs for 10, 20, 30, 40, 50, 60, 80, 90, 100, he proceeded to create this nBAB about the number 70.

   MathBabbler Number Analyst (MBNA) output:
   =========================================
   70 is a natural, whole, integer
   70 is even
   70 proper divisors are: 1,2,5,7,10,14,35,
   70 is abundant (sum of divisors is 74)
   70 is happy
   70 is a Harshad number
   70 is not prime
   70 is undulating
   70 has the prime factors: 2*5*7
   70 in octal is 0106
   70 in hexadecimal is 0x46
   70 in binary is 1000110 (is odious)
   70 nearest square numbers: -6...11 (64...81 [9])
   sqrt(70) = 8.3666
   ln(70) = 4.2485
   log(70) = 1.8451
   70 reciprocal is .01428571428571428571428571428571
   70! is 1.19786e+100
   70 is 22.2817 Pi years
   70 is 3 score and 10 years
   70 written as a Roman numeral is LXX

[Wikipedia] 70 is the smallest weird number. Reading this prompted MathBabbler to ask: What makes a number weird?

   "A weird number is a natural number that is abundant but 
    not semiperfect. In other words, the sum of the proper 
    divisors (divisors including 1 but not itself) of the 
    number is greater than the number, but no subset of 
    those divisors sums to the number itself."
   [source: Wikipedia]

OEIS.org::id:A006037

The following are the first ten weird numbers.

   70, 836, 4030, 5830, 7192, 7912, 9272, 10430, 10570, 10792

70 is the first weird number to have a nBAB created for it.

Update::2011.05.24

Bob Dylan turned 70 years young on 24 May 2011.

The MBNA had changed since this nBAB was created on 27 February 2009.

   70 is sphenic (has 3 unique prime factors)
   70 is pentagonal
   7011 is repdigit number 77

Creator: Gerald Thurman [gthurman@gmail.com]
Created: 27 February 2009

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