A prime number is a whole number divisible only by 1 and itself. Euclid in 300 B.C ... and testing a billion-digit number would take it more than 500 years. So at a minimum, he says, algorithms ...

For example, 11 is a prime number since 11 dots form only rectangular arrays of sizes 1 by 11 and 11 by 1 ... the concept of prime numbers, around 500 B.C.E. Around 300 B.C.E., the Greek ...