Prime Factorization Calculator

Prime factorization is the process of decomposing a composite number into a product of prime numbers. According to the Fundamental Theorem of Arithmetic, every integer greater than 1 can be represented uniquely as a product of prime numbers.

Step-by-Step Calculation:


How to Find Prime Factorization

To find the prime factorization of a number:

  • Step 1: Start with the smallest prime number (2).
  • Step 2: If divisible, divide and repeat.
  • Step 3: If not, try the next prime (3, 5, 7, 11...).
  • Step 4: Continue until the quotient is 1.

Common Prime Factorizations

Here is a table of common numbers and their prime factorizations:

Number Prime Factorization Is Prime?
1 1 Yes
2 2 Yes
3 3 Yes
4 2 × 2 No
5 5 Yes
6 2 × 3 No
7 7 Yes
8 2 × 2 × 2 No
9 3 × 3 No
10 2 × 5 No
11 11 Yes
12 2 × 2 × 3 No
13 13 Yes
14 2 × 7 No
15 3 × 5 No
16 2 × 2 × 2 × 2 No
18 2 × 3 × 3 No
19 19 Yes
20 2 × 2 × 5 No
21 3 × 7 No
22 2 × 11 No
23 23 Yes
24 2 × 2 × 2 × 3 No
25 5 × 5 No
26 2 × 13 No
27 3 × 3 × 3 No
28 2 × 2 × 7 No
29 29 Yes
30 2 × 3 × 5 No
31 31 Yes
32 2 × 2 × 2 × 2 × 2 No
33 3 × 11 No
34 2 × 17 No
35 5 × 7 No
36 2 × 2 × 3 × 3 No
37 37 Yes
38 2 × 19 No
39 3 × 13 No
40 2 × 2 × 2 × 5 No
41 41 Yes
42 2 × 3 × 7 No
44 2 × 2 × 11 No
45 3 × 3 × 5 No
46 2 × 23 No
47 47 Yes
48 2 × 2 × 2 × 2 × 3 No
49 7 × 7 No
50 2 × 5 × 5 No
51 3 × 17 No
52 2 × 2 × 13 No
53 53 Yes
54 2 × 3 × 3 × 3 No
55 5 × 11 No
56 2 × 2 × 2 × 7 No
57 3 × 19 No
58 2 × 29 No
59 59 Yes
60 2 × 2 × 3 × 5 No
61 61 Yes
62 2 × 31 No
63 3 × 3 × 7 No
64 2 × 2 × 2 × 2 × 2 × 2 No
65 5 × 13 No
66 2 × 3 × 11 No
67 67 Yes
68 2 × 2 × 17 No
69 3 × 23 No
70 2 × 5 × 7 No
71 71 Yes
72 2 × 2 × 2 × 3 × 3 No
73 73 Yes
74 2 × 37 No
75 3 × 5 × 5 No
76 2 × 2 × 19 No
77 7 × 11 No
78 2 × 3 × 13 No
79 79 Yes
80 2 × 2 × 2 × 2 × 5 No
81 3 × 3 × 3 × 3 No
83 83 Yes
84 2 × 2 × 3 × 7 No
85 5 × 17 No
86 2 × 43 No
87 3 × 29 No
88 2 × 2 × 2 × 11 No
90 2 × 3 × 3 × 5 No
91 7 × 13 No
92 2 × 2 × 23 No
93 3 × 31 No
94 2 × 47 No
95 5 × 19 No
96 2 × 2 × 2 × 2 × 2 × 3 No
97 97 Yes
98 2 × 7 × 7 No
99 3 × 3 × 11 No
100 2 × 2 × 5 × 5 No
101 101 Yes
102 2 × 3 × 17 No
104 2 × 2 × 2 × 13 No
105 3 × 5 × 7 No
108 2 × 2 × 3 × 3 × 3 No
110 2 × 5 × 11 No
111 3 × 37 No
112 2 × 2 × 2 × 2 × 7 No
114 2 × 3 × 19 No
115 5 × 23 No
119 7 × 17 No
120 2 × 2 × 2 × 3 × 5 No
121 11 × 11 No
123 3 × 41 No
124 2 × 2 × 31 No
125 5 × 5 × 5 No
126 2 × 3 × 3 × 7 No
128 2 × 2 × 2 × 2 × 2 × 2 × 2 No
130 2 × 5 × 13 No
132 2 × 2 × 3 × 11 No
133 7 × 19 No
135 3 × 3 × 3 × 5 No
136 2 × 2 × 2 × 17 No
138 2 × 3 × 23 No
140 2 × 2 × 5 × 7 No
143 11 × 13 No
144 2 × 2 × 2 × 2 × 3 × 3 No
147 3 × 7 × 7 No
150 2 × 3 × 5 × 5 No
152 2 × 2 × 2 × 19 No
153 3 × 3 × 17 No
154 2 × 7 × 11 No
160 2 × 2 × 2 × 2 × 2 × 5 No
162 2 × 3 × 3 × 3 × 3 No
165 3 × 5 × 11 No
168 2 × 2 × 2 × 3 × 7 No
169 13 × 13 No
171 3 × 3 × 19 No
175 5 × 5 × 7 No
176 2 × 2 × 2 × 2 × 11 No
180 2 × 2 × 3 × 3 × 5 No
182 2 × 7 × 13 No
184 2 × 2 × 2 × 23 No
186 2 × 3 × 31 No
187 11 × 17 No
189 3 × 3 × 3 × 7 No
192 2 × 2 × 2 × 2 × 2 × 2 × 3 No
195 3 × 5 × 13 No
196 2 × 2 × 7 × 7 No
198 2 × 3 × 3 × 11 No
200 2 × 2 × 2 × 5 × 5 No
204 2 × 2 × 3 × 17 No
205 5 × 41 No
207 3 × 3 × 23 No
210 2 × 3 × 5 × 7 No
212 2 × 2 × 53 No
216 2 × 2 × 2 × 3 × 3 × 3 No
220 2 × 2 × 5 × 11 No
221 13 × 17 No
224 2 × 2 × 2 × 2 × 2 × 7 No
225 3 × 3 × 5 × 5 No
230 2 × 5 × 23 No
232 2 × 2 × 2 × 29 No
240 2 × 2 × 2 × 2 × 3 × 5 No
242 2 × 11 × 11 No
243 3 × 3 × 3 × 3 × 3 No
245 5 × 7 × 7 No
248 2 × 2 × 2 × 31 No
250 2 × 5 × 5 × 5 No
252 2 × 2 × 3 × 3 × 7 No
255 3 × 5 × 17 No
256 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 No
260 2 × 2 × 5 × 13 No
264 2 × 2 × 2 × 3 × 11 No
270 2 × 3 × 3 × 3 × 5 No
273 3 × 7 × 13 No
275 5 × 5 × 11 No
280 2 × 2 × 2 × 5 × 7 No
285 3 × 5 × 19 No
286 2 × 11 × 13 No
288 2 × 2 × 2 × 2 × 2 × 3 × 3 No
293 293 Yes
294 2 × 3 × 7 × 7 No
297 3 × 3 × 3 × 11 No
300 2 × 2 × 3 × 5 × 5 No
308 2 × 2 × 7 × 11 No
310 2 × 5 × 31 No
312 2 × 2 × 2 × 3 × 13 No
315 3 × 3 × 5 × 7 No
320 2 × 2 × 2 × 2 × 2 × 2 × 5 No
324 2 × 2 × 3 × 3 × 3 × 3 No
325 5 × 5 × 13 No
330 2 × 3 × 5 × 11 No
336 2 × 2 × 2 × 2 × 3 × 7 No
350 2 × 5 × 5 × 7 No
351 3 × 3 × 3 × 13 No
360 2 × 2 × 2 × 3 × 3 × 5 No
364 2 × 2 × 7 × 13 No
375 3 × 5 × 5 × 5 No
378 2 × 3 × 3 × 3 × 7 No
385 5 × 7 × 11 No
392 2 × 2 × 2 × 7 × 7 No
396 2 × 2 × 3 × 3 × 11 No
400 2 × 2 × 2 × 2 × 5 × 5 No
420 2 × 2 × 3 × 5 × 7 No
425 5 × 5 × 17 No
432 2 × 2 × 2 × 2 × 3 × 3 × 3 No
440 2 × 2 × 2 × 5 × 11 No
441 3 × 3 × 7 × 7 No
450 2 × 3 × 3 × 5 × 5 No
462 2 × 3 × 7 × 11 No
468 2 × 2 × 3 × 3 × 13 No
480 2 × 2 × 2 × 2 × 2 × 3 × 5 No
495 3 × 3 × 5 × 11 No
500 2 × 2 × 5 × 5 × 5 No
504 2 × 2 × 2 × 3 × 3 × 7 No
510 2 × 3 × 5 × 17 No
525 3 × 5 × 5 × 7 No
528 2 × 2 × 2 × 2 × 3 × 11 No
539 7 × 7 × 11 No
540 2 × 2 × 3 × 3 × 3 × 5 No
560 2 × 2 × 2 × 2 × 5 × 7 No
572 2 × 2 × 11 × 13 No
585 3 × 3 × 5 × 13 No
588 2 × 2 × 3 × 7 × 7 No
600 2 × 2 × 2 × 3 × 5 × 5 No
612 2 × 2 × 3 × 3 × 17 No
625 5 × 5 × 5 × 5 No
630 2 × 3 × 3 × 5 × 7 No
675 3 × 3 × 3 × 5 × 5 No
676 2 × 2 × 13 × 13 No
684 2 × 2 × 3 × 3 × 19 No
700 2 × 2 × 5 × 5 × 7 No
720 2 × 2 × 2 × 2 × 3 × 3 × 5 No
760 2 × 2 × 2 × 5 × 19 No
770 2 × 5 × 7 × 11 No
792 2 × 2 × 2 × 3 × 3 × 11 No
828 2 × 2 × 3 × 3 × 23 No
875 5 × 5 × 5 × 7 No
880 2 × 2 × 2 × 2 × 5 × 11 No
891 3 × 3 × 3 × 3 × 11 No
900 2 × 2 × 3 × 3 × 5 × 5 No
980 2 × 2 × 5 × 7 × 7 No
1001 7 × 11 × 13 No
1155 3 × 5 × 7 × 11 No
1260 2 × 2 × 3 × 3 × 5 × 7 No
1287 3 × 3 × 11 × 13 No
1575 3 × 3 × 5 × 5 × 7 No
1700 2 × 2 × 5 × 5 × 17 No
2016 2 × 2 × 2 × 2 × 2 × 3 × 3 × 7 No
2017 2017 Yes
2018 2 × 1009 No
2019 3 × 673 No
2020 2 × 2 × 5 × 101 No
2021 43 × 47 No
2022 2 × 3 × 337 No
2023 7 × 17 × 17 No
2024 2 × 2 × 2 × 11 × 23 No
2205 3 × 3 × 5 × 7 × 7 No
2800 2 × 2 × 2 × 2 × 5 × 5 × 7 No
10000 2 × 2 × 2 × 2 × 5 × 5 × 5 × 5 No

The Factor Tree Method

A factor tree is a diagram that helps visualize the process of prime factorization. Write the number at the top, then draw two branches to any pair of factors. Continue branching each composite number until every endpoint is a prime. For example, for 60: split into 6 and 10, then 6 into 2 and 3, and 10 into 2 and 5. The primes are 2, 2, 3, and 5, so 60 = 2 squared x 3 x 5.

Step-by-Step Guide to Using This Calculator

Enter any positive integer greater than 1 in the Number field and click Calculate. The calculator will display whether the number is prime or composite, list all prime factors, show the total number of divisors, and provide a complete factor list. Use the Clear button to enter a new number. The step-by-step panel walks through the division method used to find the result.

Fundamental Theorem of Arithmetic

This theorem guarantees that every integer greater than 1 can be expressed as a product of prime numbers in exactly one way, apart from the order of the factors. This uniqueness is what makes prime factorization so powerful and reliable. Whether you use a factor tree, trial division, or any other valid method, you will always arrive at the same set of prime factors for any given number.

Applications in Mathematics and Beyond

Prime factorization is essential for finding the Greatest Common Factor and Least Common Multiple of numbers, which are needed for fraction arithmetic. In cryptography, the security of RSA encryption depends on the computational difficulty of factoring large semiprimes. Hash functions and random number generators also rely on properties of prime numbers. Understanding prime factorization builds strong foundations for algebra, number theory, and computer science.

Tips and Common Mistakes

Always start with the smallest prime (2) when using trial division. Do not include 1 in your factorization since it is not prime. Check your work by multiplying the prime factors back together. Remember that if no prime up to the square root of n divides n, then n itself is prime. Practice with small numbers first to build intuition before tackling larger values.

Conclusion

Prime factorization is a cornerstone of number theory with applications in cryptography, computer science, and everyday mathematics. Understanding how to decompose numbers into their prime factors is essential for many mathematical operations and real-world problem solving.

Frequently Asked Questions

The prime factorization of 84 is 2 x 2 x 3 x 7, which can be written as 2 squared x 3 x 7. To find this, divide 84 by 2 to get 42, divide 42 by 2 to get 21, divide 21 by 3 to get 7, and 7 is prime.

The prime factorization of 36 is 2 x 2 x 3 x 3, or 2 squared x 3 squared. You can find this by dividing 36 by 2 to get 18, then 18 by 2 to get 9, then 9 by 3 to get 3, and 3 is prime.

No, 1 is not considered a prime number. By definition, a prime number must have exactly two distinct positive divisors: 1 and itself. Since 1 only has one divisor (itself), it does not qualify. Excluding 1 from the primes preserves the uniqueness of prime factorization stated in the Fundamental Theorem of Arithmetic.

Start with the number at the top and split it into any two factors. Keep splitting each composite factor into smaller factors until every branch ends with a prime number. The prime numbers at the end of all branches, multiplied together, give the prime factorization. The order may vary but the result is always the same.

The prime factorization of 100 is 2 x 2 x 5 x 5, or 2 squared x 5 squared. Divide 100 by 2 to get 50, then 50 by 2 to get 25, then 25 by 5 to get 5, and 5 is prime. Multiply back: 2 x 2 x 5 x 5 = 100.

Modern encryption like RSA relies on the fact that multiplying two large primes is easy, but factoring their product back into primes is extremely difficult. This asymmetry allows secure public-key encryption where anyone can encrypt a message but only the holder of the private key (the prime factors) can decrypt it efficiently.

The prime factorization of 72 is 2 x 2 x 2 x 3 x 3, or 2 cubed x 3 squared. Using the division method: 72 divided by 2 is 36, divided by 2 is 18, divided by 2 is 9, divided by 3 is 3, and 3 is prime.

No, a prime number cannot be broken down into smaller prime factors because it is already prime. Its only factors are 1 and itself, and since 1 is not a prime number, the prime factorization of a prime number is simply the number itself. For example, the prime factorization of 13 is just 13.