2006-09-21 06:09:36 · 6 answers · asked by Purplepassion9126 2 in Science & Mathematics ➔ Mathematics
Finding large prime numbers is a difficult and specialized branch of mathematics. Because of that, you will need to find large primes that have already beed discovered. The method of using 2 primes of 200 digits each is almost correct. Be careful though since 2 small 200 digit primes will produce a 399 digit number. The easiest way to tell is to express the primes in scientific notation. Look at two hundred digit numbers: 1 x 10^199 and 2 x 10^199 (these are each 200 digits - a 1 with 199 zeroes and 2 with 199 zeroes - but not prime) multiply them together and you get 6 x 10^398 which is a 399 digit number. To get a 400 digit number from two 200 digit numbers, the mantissas must be large enough for you to carry a digit over during multiplication.
Another way to do this is to find a prime that is nearly 400 digits and multiply it by a suitably smaller prime. The Mersenne Primes are a good source for the big number. The 15th Mersenne Prime is 2^1279 - 1 = 1.041 x 10^385 at 386 digits ( http://primes.utm.edu/mersenne/index.html#known)
Now you need a prime with a 10^14 exponent or a 15 digit prime to multiply, I found 112272535095293 or 1.123 x 10^14 (http://www.alpertron.com.ar/googol.pl?digits=16) but there are plenty more around. Multiplying these together gives 1.169 x 10^399 which is a 400 digit number.
2006-09-21 09:19:00 · answer #1 · answered by Pretzels 5 · 0⤊ 0⤋
how about 1 and a 400 digit prime number
2006-09-21 13:11:45 · answer #2 · answered by bobobob 4 · 0⤊ 2⤋
Fatima B is wrong. 2 is a prime number. It is the lowest prime number.
2006-09-21 14:57:20 · answer #3 · answered by Andrew W 4 · 1⤊ 0⤋
29072553456409183479268752003825253455672839222789445223234915115682921921621182714164684048719891059149763352939888629001652768286998932224000980861127751097886364432307005283784155195197202827350411
and
58021664585639791181184025950440248398226136069516938232493687505822471836536824298822733710342250697739996825938232641940670857624514103125986134050997697160127301547995788468137887651823707102007839
http://primes.utm.edu/lists/small/small2.html#200
go to the 200 digit primes and pick them out
btw don't forget to thank me! This is moe and I'm mean!
2006-09-21 13:38:19 · answer #4 · answered by Anonymous · 0⤊ 0⤋
mmm...... 1is not a prime number, neither is 2 prime numbers are 3,5,7,11,13,17,19,e.t.c.
o i guess the number you ar looking for has to end with a prime number
but check ur question cause i dont know how on earth u are going to get two prime numbers whose product is a 400 digit number!!!!!!!!!!!!!!!!!!!!!!
2006-09-21 13:25:35 · answer #5 · answered by fatima b 4 · 0⤊ 2⤋
http://primes.utm.edu/
Doug
2006-09-21 13:14:17 · answer #6 · answered by doug_donaghue 7 · 0⤊ 0⤋