# Monthly Archives: November 2012

## Num3er 1588

Marin Mersenne   (8 September 1588 – 1 September 1648)     The factors of   1588   are:      1    2    4    397    794    1588 The prime factors are:      2 * 2 * … Continue reading

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## Num3ers that are divisible by 2-digit numbers contained in them

For example, 132         132 / 12 = 11 135         135 / 15 = 9 612         612 / 12 = 51 and many others. They are not very interesting since they are only divisible by one 2-digit number … Continue reading

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## Sum of even positive squares

2^2 + 4^2 = 4*5 2^2 + 4^2 + 6^2 + 8^2 + 10^2 = 4*5 + 5*6 + 6*7 + 7*8 + 8*9   we see that in these two cases that the sum of even positive squares … Continue reading

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## Repeating decimal 0.19 and 0.199

0.19   stands for the repeating decimal   (= 19/99): 0.1919191919191919191919191919191919191919191919191919… and   0.199   for   (= 199/999) 0.1991991991991991991991991991991991991991991991991991…   0.19   +   0.199   =   19/99   +   199/999   =   391118/999999 that is, … Continue reading

## Concatenation puzzle: when (A || B) / B is an integer

Concatenation is the joining of two numbers by their numerals. That is, the concatenation of   444   and   777   is   444777. Concatenation of numbers   A   and   B   is denoted   A || … Continue reading

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## Can You Crack Pigeon’s Secret Wartime Code?

LONDON (Reuters) – A World War Two code found strapped to the leg of a dead pigeon stuck in a chimney for the last 70 years may never be broken, a British intelligence agency said on Friday. Watch the Reuters … Continue reading

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## Num3er 1170

Leonardo Pisano Fibonacci   1170 – 1250     The factors of   1170   are:     1   2   3   5   6   9   10   13   15   18   26   30 … Continue reading

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## Num3er 1913

Paul Erdős   1913 – 1996 The year in which mathematician Paul Erdős was born is an emirp.   1913   is the smallest prime p such that its next prime (1931) is an anagram of p An emirp (“prime” … Continue reading

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## Pythagorean triple – Digits Reversed

Pythagorean triple – Definition: A Pythagorean triple consists of three positive integers a, b, and c, such that                                      a^2 + b^2 = c^2 (33, 56, 65)   is one example of a primitive Pythagorean triangle in which the … Continue reading

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## Num3er 75

The factors of   75   are:     1   3   5   15   25   75 The prime factors are:     3 * 5 * 5   75   is 1001011   in base 2 2210   … Continue reading

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