Prime and Composite Number Checker

Welcome to use the Prime and Composite Number Checker, which can quickly help you verify whether the number is prime or composite.

Prime and Composite Number Checker

Eg, Is 99 prime or composite? Enter 99 into the input box and click Calculate button.

Calculate Reset

Definition of prime and composite numbers

A prime number is a natural number that has no factors other than 1 and itself among the natural numbers greater than 1. For example, both 3 and 7 are prime numbers with no factors other than 1 and themselves.

The opposite of a prime number is called a composite number, that is, an integer greater than 1, which is divisible by other numbers besides 1 and itself. For example, 4 and 10 are composite numbers.

Note that prime and composite numbers apply to integers greater than 1, so 1 is neither prime nor composite.

When judging whether a number is prime or composite, the key is to count the number of its factors. If there are only two factors, in other words, only 1 and itself, then the number is prime. If the number of factors is greater than 2, then the number is composite.

First 100 Prime Numbers

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

First 100 Composite Numbers

4	6	8	9	10	12	14	15	16	18
20	21	22	24	25	26	27	28	30	32
33	34	35	36	38	39	40	42	44	45
46	48	49	50	51	52	54	55	56	57
58	60	62	63	64	65	66	68	69	70
72	74	75	76	77	78	80	81	82	84
85	86	87	88	90	91	92	93	94	95
96	98	99	100	102	104	105	106	108	110
111	112	114	115	116	117	118	119	120	121
122	123	124	125	126	128	129	130	132	133

How to use the prime and composite number checker

The procedure to use the prime and composite number checker is as follows:

1Enter the positive integer.
2Click Calculate button to check whether the input integer is prime or composite.
3Click the Reset button to start a new check.

Solved examples using the prime and composite number checker

Example 1: Is 17 prime or composite?

Enter 17 into the input box and click Calculate button, as shown in the figure, the factors of 17 are 1 and 17. So, 17 is a prime number.

Example 2: Is 87 prime or composite?

Enter 87 into the input box and click Calculate button, as shown in the figure, the factors of 87 are 1, 3, 29 and 87. So, 87 is a composite number.

Example 3: Is 91 prime or composite?

Enter 91 into the input box and click Calculate button, as shown in the figure, the factors of 91 are 1, 7, 13 and 91. So, 91 is a composite number.

Prime and Composite Number Checker