Divisors of the Positive Integer 21

1, 3, 7, 21

Sum of all the Divisors of 21, including itself

32

Sum of the Proper Divisors of 21

11

Properties of the number 21

The integer 21 is an odd number.
The integer 21 is a Composite number.
11 is less than 21, so 21 is a deficient number.

The number 21 as a Roman Numeral

XXI

The number 21 in various Numeral Systems

Base Representation
2:10101
3:210
4:111
5:41
6:33
7:30
8:25
9:23
10:21
11:1A
12:19
13:18
14:17
15:16
16:15
17:14
18:13
19:12
20:11
21:10
22:L
23:L
24:L
25:L
26:L
27:L
28:L
29:L
30:L
31:L
32:L
33:L
34:L
35:L
36:L