Prime Numbers
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Numbers
Compare 5 vs 21
Compare 5 vs 21
Compare
vs
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Property
5
21
Type
prime
semiprime
Unique factors
1
2
Total factors
1
2
Prime factorization
5
^{1}
3
^{1}
×
7
^{1}
Prime factorization
5
3
×
7
Divisors count
2
4
Divisors
1
,
5
1
,
3
,
7
,
21
Number of properties
36
1
Additive primes
3rd
Bell primes
2nd
Centered square primes
1st
Chen primes
3rd
Class 1+ primes
3rd
Dihedral primes
2nd
Factorial primes
3rd
Fermat primes
2nd
Fibonacci primes
3rd
Good primes
1st
Harmonic primes
1st
Left-truncatable primes
3rd
Multiplicative primes
3rd
Palindromic primes
3rd
Pierpont primes
3rd
Pierpont primes of the 2nd kind
3rd
Primes
3rd
Prime quadruplets
(1st member)
1st
Prime quintuplet 2s
(1st member)
1st
Prime triplets
(1st member)
1st
Proth primes
2nd
Pythagorean primes
1st
Restricted left-truncatable primes
2nd
Right-truncatable primes
3rd
Safe primes
1st
Semiprimes
7th
Sexy primes
(1st member)
1st
Sexy prime quadrupletss
(1st member)
1st
Sexy prime triplets
(1st member)
1st
Solinas primes
2nd
Sophie germain primes
3rd
Super primes
2nd
Thabit primes
2nd
Twin primes
(1st member)
2nd
Twin primes
(2nd member)
1st
Two-sided primes
3rd
Wilson primes
1st
Roman numberals
V
XXI
Base 2
101
_{2}
10101
_{2}
Base 3
12
_{3}
210
_{3}
Base 4
11
_{4}
111
_{4}
Base 5
10
_{5}
41
_{5}
Base 6
5
_{6}
33
_{6}
Base 7
5
_{7}
30
_{7}
Base 8
5
_{8}
25
_{8}
Base 9
5
_{9}
23
_{9}
Base 10
5
_{10}
21
_{10}
Base 11
5
_{11}
1a
_{11}
Base 12
5
_{12}
19
_{12}
Base 13
5
_{13}
18
_{13}
Base 14
5
_{14}
17
_{14}
Base 15
5
_{15}
16
_{15}
Base 16
5
_{16}
15
_{16}
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