21 Quaternary to Binary
21 quaternary = 1001 binary
21 written in binary is 1001, the number 9 in everyday decimal.
21 quaternary = 1001 binary
How to convert 21 to binary
Step 1: Quaternary to decimal
Multiply each digit by 4 to the power of its position (0 on the right), then add:
| Digit | Place value | Digit × place |
|---|---|---|
2 | 41 = 4 | 8 |
1 | 40 = 1 | 1 |
8 + 1 = 9
Step 2: Decimal to binary
Divide by 2 repeatedly and keep the remainders. Reading the remainders from the last one to the first gives the binary digits:
| Division | Quotient | Remainder (digit) |
|---|---|---|
| 9 ÷ 2 | 4 | 1 |
| 4 ÷ 2 | 2 | 0 |
| 2 ÷ 2 | 1 | 0 |
| 1 ÷ 2 | 0 | 1 |
Result: 9 = 1001 in binary.
21 (quaternary) in other systems
| Decimal | 9 |
| Roman numerals | IX |
| Hexadecimal | 9 |
| Octal | 11 |
| Duodecimal | 9 |
| Ternary | 100 |
| Base 36 | 9 |
| Vigesimal | 9 |
| Quinary | 14 |
| Senary | 13 |
Nearby quaternary to binary conversions
| 10 to binary | 100 |
| 11 to binary | 101 |
| 12 to binary | 110 |
| 13 to binary | 111 |
| 20 to binary | 1000 |
| 22 to binary | 1010 |
| 23 to binary | 1011 |
| 30 to binary | 1100 |
| 31 to binary | 1101 |
| 32 to binary | 1110 |
About the number 9
- 9 is an odd number.
- 9 is not a prime number.
- 9 is a perfect square: 3 × 3.
- Written in binary it needs 4 bits, so it fits in one byte.
Reverse conversion
Frequently asked questions
What is 21 in binary?
21 in quaternary is 1001 in binary (the number 9 in decimal).