It allows both the run time of the creation of the sieve and of the prime factorization to be displayed.)

Numbers may be entered as integers or as arithmetic expressions like

2^31-7

2*3*5*7 - 1

3*(5+7)*11^2

Only one exponentiation (^) may be used and parentheses may not be parsed properly
2*3*5*7 - 1

3*(5+7)*11^2

Some nice primes

30029 = 2*3*5*7*11*13 - 1

3263443 = 2*3*7*43*13*139 + 1

901830931 = 2*3*5*7*11*13*59*509 + 1 (twin with 901830929)

32464862431 = 2*3*5*7*11*13*17*19*3347+1 (twin with 32464862429)

317132017 = (2*3*5*7*11*13*17*19*23*317+1)/223

30635719141

314159 How many substrings of pi are prime?

157079632679 Half of pi

15485863 -- The one millionth prime

3263443 = 2*3*7*43*13*139 + 1

901830931 = 2*3*5*7*11*13*59*509 + 1 (twin with 901830929)

32464862431 = 2*3*5*7*11*13*17*19*3347+1 (twin with 32464862429)

317132017 = (2*3*5*7*11*13*17*19*23*317+1)/223

30635719141

314159 How many substrings of pi are prime?

157079632679 Half of pi

15485863 -- The one millionth prime