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Prime Numbers

A prime number can be divided, without a remainder, only by itself and by 1. For example, 17 can be divided only by 17 and by 1.

Some facts:

  • The only even prime number is 2. All other even numbers can be divided by 2.
  • No prime number greater than 5 ends in a 5. Any number greater than 5 that ends in a 5 can be divided by 5.
  • Zero and 1 are not considered prime numbers.
  • Except for 0 and 1, a number is either a prime number or a composite number. A composite number is defined as any number, greater than 1, that is not prime.

To prove whether a number is a prime number, first try dividing it by 2, and see if you get a whole number. If you do, it can't be a prime number. If you don't get a whole number, next try dividing it by prime numbers: 3, 5, 7, 11 (9 is divisible by 3) and so on, always dividing by a prime number (see table below).

Here is a table of all prime numbers up to 1,000:

 

2

3

5

7

11

13

17

19

23

29

31

37

41

43

47

53

59

61

67

71

73

79

83

89

97

101

103

107

109

113

127

131

137

139

149

151

157

163

167

173

179

181

191

193

197

199

211

223

227

229

233

239

241

251

257

263

269

271

277

281

283

293

307

311

313

317

331

337

347

349

353

359

367

373

379

383

389

397

401

409

419

421

431

433

439

443

449

457

461

463

467

479

487

491

499

503

509

521

523

541

547

557

563

569

571

577

587

593

599

601

607

613

617

619

631

641

643

647

653

659

661

673

677

683

691

701

709

719

727

733

739

743

751

757

761

769

773

787

797

809

811

821

823

827

829

839

853

857

859

863

877

881

883

887

907

911

919

929

937

941

947

953

967

971

977

983

991

997

 

 


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