A prime date
Posted: Mon Jan 03, 2011 6:15 pm
103 is a prime number, as is 2011. So today's a prime date. ![:) :ssmile:](./images/smilies/smile.gif)
That is all.
![:) :ssmile:](./images/smilies/smile.gif)
That is all.
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Not quite sure why 1/3/2011 or 1032011 (= 41 x 25171)owlice wrote:
103 is a prime number, as is 2011. So today's a prime date.
http://www.fourmilab.ch/yoursky/help/controls.html#Julian wrote:
<<Astronomers often have to do arithmetic with dates and times. The Gregorian calendar is sufficiently eccentric that answering a question like “What is the date and time 295.03589 days (10 lunar months) from now?” is a nontrivial exercise. To facilitate computation, astronomers employ the Julian day calendar. The Julian day number for a given moment in time is simply the number of days, whole and fractional, elapsed since noon (12:00) Universal time on 1st January −4712; time is expressed as a fraction of a day. This system allows assigning a positive number to the date and time of any observation in recorded history and arbitrarily far into the future, and permits ordinary arithmetic with dates and times without having to worry about B.C. and A.D., Julian and Gregorian calendars, leap years, and all that. Of course, you need to be able to convert back and forth between Julian days and the civil calendar, but that's what computers are for.>>
owlice wrote:
As was 01/01/2011, and is this Friday, and...
http://en.wikipedia.org/wiki/Prime_number wrote:
<<A natural number is called a prime or a prime number if it has exactly two distinct natural number divisors. Natural numbers greater than 1 that are not prime are called composite. Therefore, 1 is not prime, since it has only one divisor, namely 1. However, 2 and 3 are prime, since they have exactly two divisors, namely 1 and 2, and 1 and 3, respectively. Next, 4, is composite, since it has 3 divisors: 1, 2, and 4.
A prime number (or a prime) is a natural number that has exactly two distinct natural number divisors: 1 and itself. The smallest twenty-five prime numbers (all the prime numbers under 100) are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97.>>
Did he stop at 2?owlice wrote:
"[Name!] Count backwards from 100 by prime numbers!" And that was it -
- the crisis was averted; he was immediately and wholly engaged in the task.
I would never have thought of having him do that!
I don't know; I wasn't there, as he was at school, and I never thought to ask how far he got!neufer wrote:Did he stop at 2?
I will let him know about that site; thanks!neufer wrote:Perhaps your son would be interested in one of the free (and completely safe)
program downloads at Dmitry Brant's website:
http://dmitrybrant.com/2007/01/05/primespiral
Do we now start a discussion on whether 1 is prime?neufer wrote:1/3/2011 (or 3/1/2011) could still be said to be prime
since it is the 3rd day of 2011.
The last such day was the 359th day of 2003 (Xmas of 2003).
The first day with a prime month, day & year will be 2/3/2011
The first day with a prime day, month & year and day of the year
will be 3/7/2011 (the 67th day of the year).
owlice wrote:Do we now start a discussion on whether 1 is prime?
Wikipedia wrote:Primality of one
One of the primary reasons to exclude 1 from the set of prime numbers is the fundamental theorem of arithmetic, which says that every positive integer x can be uniquely written as a product of primes. When x is itself prime, this factorization has only one prime (x itself) in it, and when x = 1 the factorization is the empty product. But if 1 were admitted as a prime, then any integer could be factored in an infinite number of ways. For example, in this case the number 3 could be factored as 1k · 3 = 3 for any integer k.
More generally, in unique factorization domains, every non-zero element is a unique product of prime elements and a unit. The factorization would not be unique if products of units were allowed.
March 7th is the 66th day of the year.neufer wrote:The first day with a prime day, month & year and day of the year
will be 3/7/2011 (the 67th day of the year).
My bad. So what is the answer?bystander wrote:March 7th is the 66th day of the year.neufer wrote:The first day with a prime day, month & year and day of the year
will be 3/7/2011 (the 67th day of the year).
05/07/2011 - 127neufer wrote:My bad. So what is the answer?
42, of course.neufer wrote:So what is the answer?
That depends -- Are you ribs, steak or roast??owlice wrote: Do we now start a discussion on whether 1 is prime?![]()
42 isn't prime, though.owlice wrote:42, of course.neufer wrote:So what is the answer?
05/17/2011 - 137 = Julian day starting at noon: 2,455,699 (Prime)bystander wrote:05/07/2011 - 127neufer wrote:
So what is the answer?
05/11/2011 - 131
05/17/2011 - 137
05/19/2011 - 139
05/29/2011 - 149
05/31/2011 - 151
Now, that is a prime date. Need something special for that.neufer wrote:05/17/2011 - 137 = Julian day starting at noon: 2,455,699 (Prime)
That's why Three Dog Night sang that 1 is the loneliest number. It has no one but itself to go out on a date with.neufer wrote:Therefore, 1 is not prime, since it has only one divisor, namely 1.