Composite Numbers | Math Tools

What is a Composite Number?

A composite number is a positive integer that can be formed by multiplying together two smaller positive integers — a whole number that can be divided evenly by numbers other than 1 or itself. Every positive integer other than 1 is either prime or composite; 1 itself is neither.

An Example of a Composite Number

Every composite number can be written as a product of two or more (not necessarily distinct) primes. For example, 456 breaks down as:

Curious about a different number? See its prime factorization.

Types of Composite Numbers

One way to categorize composite numbers is by counting their prime factors:

Semiprime — a composite number with exactly two prime factors.
Sphenic number — a composite with three distinct prime factors.
Powerful number — every prime factor is repeated.
Squarefree — no prime factor is repeated.

Another way is by counting divisors — every composite number has at least three:

A number with more divisors than any smaller number is a highly composite number.

Meaning of a Composite Number

Meaning of a composite number

How Can You Tell if a Number is Composite or Prime?

Find all the factors of the number.
If it has only two factors — 1 and itself — it's prime.
If it has more than two factors, it's composite.

Rather do this by hand? Use the Is a Number Composite? checker.

Recognizing Prime and Composite Numbers

Recognizing prime and composite numbers

List of the First 150 Composite Numbers

#	Composite
1	4
2	6
3	8
4	9
5	10
6	12
7	14
8	15
9	16
10	18
11	20
12	21
13	22
14	24
15	25
16	26
17	27
18	28
19	30
20	32
21	33
22	34
23	35
24	36
25	38
26	39
27	40
28	42
29	44
30	45
31	46
32	48
33	49
34	50
35	51
36	52
37	54
38	55
39	56
40	57
41	58
42	60
43	62
44	63
45	64
46	65
47	66
48	68
49	69
50	70
51	72
52	74
53	75
54	76
55	77
56	78
57	80
58	81
59	82
60	84
61	85
62	86
63	87
64	88
65	90
66	91
67	92
68	93
69	94
70	95
71	96
72	98
73	99
74	100
75	102
76	104
77	105
78	106
79	108
80	110
81	111
82	112
83	114
84	115
85	116
86	117
87	118
88	119
89	120
90	121
91	122
92	123
93	124
94	125
95	126
96	128
97	129
98	130
99	132
100	133
101	134
102	135
103	136
104	138
105	140
106	141
107	142
108	143
109	144
110	145
111	146
112	147
113	148
114	150
115	152
116	153
117	154
118	155
119	156
120	158
121	159
122	160
123	161
124	162
125	164
126	165
127	166
128	168
129	169
130	170
131	171
132	172
133	174
134	175
135	176
136	177
137	178
138	180
139	182
140	183
141	184
142	185
143	186
144	187
145	188
146	189
147	190
148	192
149	194
150	195

#	Composite
1	4
2	6
3	8
4	9
5	10
6	12
7	14
8	15
9	16
10	18
11	20
12	21
13	22
14	24
15	25
16	26
17	27
18	28
19	30
20	32
21	33
22	34
23	35
24	36
25	38
26	39
27	40
28	42
29	44
30	45
31	46
32	48
33	49
34	50
35	51
36	52
37	54
38	55
39	56
40	57
41	58
42	60
43	62
44	63
45	64
46	65
47	66
48	68
49	69
50	70
51	72
52	74
53	75
54	76
55	77
56	78
57	80
58	81
59	82
60	84
61	85
62	86
63	87
64	88
65	90
66	91
67	92
68	93
69	94
70	95
71	96
72	98
73	99
74	100
75	102
76	104
77	105
78	106
79	108
80	110
81	111
82	112
83	114
84	115
85	116
86	117
87	118
88	119
89	120
90	121
91	122
92	123
93	124
94	125
95	126
96	128
97	129
98	130
99	132
100	133
101	134
102	135
103	136
104	138
105	140
106	141
107	142
108	143
109	144
110	145
111	146
112	147
113	148
114	150
115	152
116	153
117	154
118	155
119	156
120	158
121	159
122	160
123	161
124	162
125	164
126	165
127	166
128	168
129	169
130	170
131	171
132	172
133	174
134	175
135	176
136	177
137	178
138	180
139	182
140	183
141	184
142	185
143	186
144	187
145	188
146	189
147	190
148	192
149	194
150	195

#	Composite
1	4
2	6
3	8
4	9
5	10
6	12
7	14
8	15
9	16
10	18
11	20
12	21
13	22
14	24
15	25
16	26
17	27
18	28
19	30
20	32
21	33
22	34
23	35
24	36
25	38
26	39
27	40
28	42
29	44
30	45
31	46
32	48
33	49
34	50
35	51
36	52
37	54
38	55
39	56
40	57
41	58
42	60
43	62
44	63
45	64
46	65
47	66
48	68
49	69
50	70
51	72
52	74
53	75
54	76
55	77
56	78
57	80
58	81
59	82
60	84
61	85
62	86
63	87
64	88
65	90
66	91
67	92
68	93
69	94
70	95
71	96
72	98
73	99
74	100
75	102
76	104
77	105
78	106
79	108
80	110
81	111
82	112
83	114
84	115
85	116
86	117
87	118
88	119
89	120
90	121
91	122
92	123
93	124
94	125
95	126
96	128
97	129
98	130
99	132
100	133
101	134
102	135
103	136
104	138
105	140
106	141
107	142
108	143
109	144
110	145
111	146
112	147
113	148
114	150
115	152
116	153
117	154
118	155
119	156
120	158
121	159
122	160
123	161
124	162
125	164
126	165
127	166
128	168
129	169
130	170
131	171
132	172
133	174
134	175
135	176
136	177
137	178
138	180
139	182
140	183
141	184
142	185
143	186
144	187
145	188
146	189
147	190
148	192
149	194
150	195

#	Composite
1	4
2	6
3	8
4	9
5	10
6	12
7	14
8	15
9	16
10	18
11	20
12	21
13	22
14	24
15	25
16	26
17	27
18	28
19	30
20	32
21	33
22	34
23	35
24	36
25	38
26	39
27	40
28	42
29	44
30	45
31	46
32	48
33	49
34	50
35	51
36	52
37	54
38	55
39	56
40	57
41	58
42	60
43	62
44	63
45	64
46	65
47	66
48	68
49	69
50	70
51	72
52	74
53	75
54	76
55	77
56	78
57	80
58	81
59	82
60	84
61	85
62	86
63	87
64	88
65	90
66	91
67	92
68	93
69	94
70	95
71	96
72	98
73	99
74	100
75	102
76	104
77	105
78	106
79	108
80	110
81	111
82	112
83	114
84	115
85	116
86	117
87	118
88	119
89	120
90	121
91	122
92	123
93	124
94	125
95	126
96	128
97	129
98	130
99	132
100	133
101	134
102	135
103	136
104	138
105	140
106	141
107	142
108	143
109	144
110	145
111	146
112	147
113	148
114	150
115	152
116	153
117	154
118	155
119	156
120	158
121	159
122	160
123	161
124	162
125	164
126	165
127	166
128	168
129	169
130	170
131	171
132	172
133	174
134	175
135	176
136	177
137	178
138	180
139	182
140	183
141	184
142	185
143	186
144	187
145	188
146	189
147	190
148	192
149	194
150	195