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

`.`

70MathBabbler 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]`

`is the smallest`

70weird 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

`is the first`

70weird numberto have a nBAB created for it.## Update::2011.05.24

Bob Dylan turned

`years young on 24 May 2011.`

70The MBNA had changed since this nBAB was created on 27 February 2009.

70 is sphenic (has 3 unique prime factors) 70 is pentagonal 70_{11}is repdigit number 77

**Creator:** Gerald Thurman
[gthurman@gmail.com]

**Created:** 27 February 2009

This work is licensed under a Creative Commons Attribution 3.0 United States License.