Number 21
"Number Facts & Properties" Calculator
What is number 21?
Answer
Number 21 is
an odd number
Twenty-one
The last digit, 1, is odd, so 21 is odd: 21 = 2 × 10 + 1.
How to read it
Ordinal
twenty-first
Divisibility
no — composite
21 = 3 × 7
4: 1, 3, 7, 21
Nearest primes
19 and 23
Other notations
10101
Digits
Number of digits
2
Sum of digits
2 + 1 = 3
Product of digits
2 × 1 = 2
Codes
QR code
Barcode (Code 128)
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See Also
- Decimal to Binary Converter - Decimal numbers to Binary conversion
- Numbers to Roman Numerals - Decimal numbers to Roman numerals conversion
- Factors of a Number - List all Factors and Factor Pairs of a Number
- Prime Number Checker - Find out whether a given number is Prime or not
- Prime Factorization - Prime Factorization Calculator
- Prime Numbers List - List of all Prime Numbers - how many Prime numbers are between
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