Tagged: numbers

Paul Erdős

After reading The Man Who Loved Only Numbers: The Story of Paul Erdős and the Search for Mathematical Truth this summer, I came across a fantastic children’s book about Paul Erdős.  The Boy Who Loved Math: The Improbable Life of Paul Erdős by Deborah Heiligman with pictures by LeUyen Pham is an excellent introduction to the man who is well-known for his collaboration in mathematics.  Below is a photo of the cover and my favorite illustration in the book:

IMG_1232   IMG_1236

Below is a short clip from N is a Number, which is a fantastic glimpse of Paul Erdős and his life of collaboration in mathematics:

References:

Heiligman, D. (2013). The boy who loved math: The improbable life of Paul Erdős. New York: Roaring Brook Press.

Hoffman, P. (1998). The man who loved only numbers: The story of Paul Erdős and the search for mathematical truth. New York: Hyperion.

smith numbers

Prime numbers have been a popular topic in the news.  Below is a strip about working with composite and prime numbers, using what are called Smith Numbers.  Smith Numbers are composite, but identified when the sum of the individual digits in the number are equal to the sum of the prime factors!

Now let’s take a look at 27.  The number 27 is probably most easily identified by school children as being 9 • 3. However, 9 is composite, so instead let’s take the 9 and look at it as 3 • 3.  Now we have 27 taken as 2 + 7, which is 9, and 3 + 3 + 3, which is also 9.

For the number 27: 2 + 7 = 3 + 3 + 3

Can 71 be a Smith Number?

References:

Caldwell, C. (2013). Smith number from The Prime Glossary http://primes.utm.edu/glossary/xpage/SmithNumber.html Accessed 11 June 2013.

Hoffman, P. (1998). The man who loved only numbers: The story of Paul Erdos and the search for mathematical truth. New York: Hyperion.

Weisstein, Eric W. “Smith Number.” From MathWorld–A Wolfram Web Resource. http://mathworld.wolfram.com/SmithNumber.html Accessed 11 June 2013.

another black hole number: 123

The black hole number 4 has been previously discussed here.  Below is a look at the black hole number 123 (click the image for a larger view):

*Another interesting note: In Italian, the number 3 (tre) is a black hole number.

Recently, Cliff Pickover tweeted about the number 4 being the only number in English have the same number of letters as its value.  I tweeted a response that in Danish this is true for the numbers 2, 3, and 4 (to, tre, fire). These numbers are often referred to as honest numbers, which are related to black hole numbers. Also, there are honest expressions such as this one:

This honest expression was created by Michael Burke.

References:

Ecker, M. Number play, calculators, and card tricks: Mathemagical black holes. Retrieved from http://g4gardner.pbworks.com/f/mm-ecker.pdf

Gardner, M. (1976). The incredible dr. matrix. New York: Charles Scribner’s Sons.

O’Shea, O. & Dudley, U. (2007). The magic numbers of the professor. Washington, DC: The Mathematical Association of America, Inc.