Number reference
53 explained.
53: fifty-three, prime; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- fifty-three
- Classification
- prime
- Factors
- 1, 53
- Prime factorization
- 53
- Square root
- 7.28011
- Cube root
- 3.756286
- Binary
- 110101
- Octal
- 65
- Hexadecimal
- 35
- Roman numeral
- LIII
- Digit sum
- 8
- Digital root
- 8
What makes 53 notable
- Prime. 53 is prime: it has exactly two divisors, 1 and itself, so it cannot be split into equal whole-number groups any other way.
53 in everyday use
Fifty-three is the atomic number of iodine, the element added to table salt to prevent thyroid disease. Some years contain 53 numbered weeks under the ISO calendar, whenever 1 January falls on a Thursday or a leap year starts on a Wednesday. Herbie, the Volkswagen Beetle of Disney's The Love Bug, raced under the number 53. The standard semi-trailer in US trucking is 53 feet long.
Fifty-three is the sixteenth prime, the sum of two squares 4 + 49, and a Sophie Germain prime, since 2 × 53 + 1 = 107 is also prime. It has a neat coincidence: in hexadecimal it is written 35, its own digits reversed. Fifty-three is also the sum of five consecutive primes, 5 + 7 + 11 + 13 + 17. Neither 51 nor 55 is prime, so it is an isolated prime.
Nearby numbers
How to read this page
Because 53 is prime, the factor list stops at 1 and 53 itself, so it cannot be shared into equal whole-number groups. That is also what makes it useful as a building block: every larger number with 53 in its prime factorisation inherits it from here.
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