21 in Binary
Decimal 21 equals 10101 in binary.
21 in all number bases
Decimal21
Hexadecimal0x15
Binary0001 0101
Octal25
How 21 converts from decimal to binary
Divide by 2 repeatedly and keep each remainder, then read the remainders from bottom to top:
21÷ 2 =10remainder1
10÷ 2 =5remainder0
5÷ 2 =2remainder1
2÷ 2 =1remainder0
1÷ 2 =0remainder1
Result (remainders bottom to top): 10101