Most early Greeks did not even consider 1 to be a number, so they could not consider it to be a prime. By the Middle Ages and Renaissance many mathematicians included 1 as the first prime number. In the mid-18th century Christian Goldbach listed 1 as the first prime in his famous correspondence with Leonhard Euler -- who did not agree. In the 19th century many mathematicians still considered the number 1 to be a prime. For example, Derrick Norman Lehmer's list of primes up to 10,006,721, reprinted as late as 1956, started with 1 as its first prime. Henri Lebesgue is said to be the last professional mathematician to call 1 prime. By the early 20th century, mathematicians began to accept that 1 is not a prime number, but rather forms its own special category as a "unit".
How many primes were included in Derrick Norman Lehmer's list of prime numbers?
10,006,721 primes up to 10,006,721 10,006,721 10,006,721 10,006,721
For example, Derrick Norman Lehmer's list of primes up to 10,006,721, reprinted as late as 1956, started with 1 as its first prime.
For example, Derrick Norman Lehmer's list of primes up to ten million, six thousand, seven hundred twenty-one, reprinted as late as nineteen fifty-six, started with one as its first prime.
How many primes were included in Derrick Norman Lehmer's list of prime numbers?