Number 21

Representations of 21
Greek numeral
καʹ
Sanskrit numeral
२१
Arabic numeral
٢١
Roman numeral
XXI
Maya numeral
●
●
Chinese numeral
二十一
Hebrew numeral
כא
21 in different numeral systems
Binary
10101
Base-3
210
Base-4
111
Base-5
41
Base-6
33
Base-7
30
Base-8
25
Duodecimal
19
Hex
15
Vigesimal
11
Base-24
l
Base-36
l
Negabinary
10101
Factorization
Prime factors
3, 7
Divisors
1, 3, 7, 21
Sum of divisors other than 21
11
Product of prime factors
21 = 3 x 7
Characteristics
Triangular Octogonal Difference of 2 squares Harshad One O Odd Fibonacci Composite Deficient
Related primes
Number 21 prime
73
Prime number before 21
19
Prime number after 21
23