about Numbers...

bandung 24.07.00
11.40 pm


Fundamental Theorem of Arithmetic
Any positive integer (except 1) can be written as the product of prime numbers in one and only one way.

Erdos numbers [Paul Erdos, Hungarian math]
"Between any whole numbers n and 2n, there must always lie at least one prime" (at his 17 years old... omg!)

Amicable numbers [Leonhard Euler, 18th century]
"two whole numbers to be amicable if each was the sum of the proper divisors of the other"

example:
220 = 1,2,4,5,10,11,20,22,44,55,110,220 (the divisors of 220)
284 = 1,2,4,71,142,284 (the divisors of 284)

then
220 = 1+2+4+71+142
284 = 1+2+4+5+10+11+20+22+44+55+110