Definition
2 is the only even prime. 1 is not prime, because a prime must have exactly two distinct positive divisors. Numbers greater than 1 that are not prime are composite.
By the fundamental theorem of arithmetic, every integer greater than 1 is a product of primes in exactly one way, apart from the order of the factors. There are infinitely many primes (Euclid).
Sources: OpenStax: Contemporary Mathematics §3.1 Prime and Composite Numbers; NIST Digital Library of Mathematical Functions: DLMF §27.2 Functions of Number Theory (primes)
The first 200 prime numbers
The 200th prime is 1223. The first 168 entries are exactly the primes below 1000, ending at 997.
| # | +0 | +1 | +2 | +3 | +4 | +5 | +6 | +7 | +8 | +9 |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 5 | 7 | 11 | 13 | 17 | 19 | 23 | 29 |
| 11 | 31 | 37 | 41 | 43 | 47 | 53 | 59 | 61 | 67 | 71 |
| 21 | 73 | 79 | 83 | 89 | 97 | 101 | 103 | 107 | 109 | 113 |
| 31 | 127 | 131 | 137 | 139 | 149 | 151 | 157 | 163 | 167 | 173 |
| 41 | 179 | 181 | 191 | 193 | 197 | 199 | 211 | 223 | 227 | 229 |
| 51 | 233 | 239 | 241 | 251 | 257 | 263 | 269 | 271 | 277 | 281 |
| 61 | 283 | 293 | 307 | 311 | 313 | 317 | 331 | 337 | 347 | 349 |
| 71 | 353 | 359 | 367 | 373 | 379 | 383 | 389 | 397 | 401 | 409 |
| 81 | 419 | 421 | 431 | 433 | 439 | 443 | 449 | 457 | 461 | 463 |
| 91 | 467 | 479 | 487 | 491 | 499 | 503 | 509 | 521 | 523 | 541 |
| 101 | 547 | 557 | 563 | 569 | 571 | 577 | 587 | 593 | 599 | 601 |
| 111 | 607 | 613 | 617 | 619 | 631 | 641 | 643 | 647 | 653 | 659 |
| 121 | 661 | 673 | 677 | 683 | 691 | 701 | 709 | 719 | 727 | 733 |
| 131 | 739 | 743 | 751 | 757 | 761 | 769 | 773 | 787 | 797 | 809 |
| 141 | 811 | 821 | 823 | 827 | 829 | 839 | 853 | 857 | 859 | 863 |
| 151 | 877 | 881 | 883 | 887 | 907 | 911 | 919 | 929 | 937 | 941 |
| 161 | 947 | 953 | 967 | 971 | 977 | 983 | 991 | 997 | 1009 | 1013 |
| 171 | 1019 | 1021 | 1031 | 1033 | 1039 | 1049 | 1051 | 1061 | 1063 | 1069 |
| 181 | 1087 | 1091 | 1093 | 1097 | 1103 | 1109 | 1117 | 1123 | 1129 | 1151 |
| 191 | 1153 | 1163 | 1171 | 1181 | 1187 | 1193 | 1201 | 1213 | 1217 | 1223 |
How many primes there are
π(x) counts the primes up to x. The prime number theorem says π(x) is approximately x ÷ ln x for large x.
| x | π(x) | x ÷ ln x |
|---|---|---|
| 10 | 4 | 4.3 |
| 100 | 25 | 21.7 |
| 500 | 95 | 80.5 |
| 1,000 | 168 | 144.8 |