Number reference
71 explained.
71: seventy-one, prime; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- seventy-one
- Classification
- prime
- Factors
- 1, 71
- Prime factorization
- 71
- Square root
- 8.42615
- Cube root
- 4.140818
- Binary
- 1000111
- Octal
- 107
- Hexadecimal
- 47
- Roman numeral
- LXXI
- Digit sum
- 8
- Digital root
- 8
What makes 71 notable
- Prime. 71 is prime: it has exactly two divisors, 1 and itself, so it cannot be split into equal whole-number groups any other way.
71 in everyday use
Seventy-one is the atomic number of lutetium, the last of the lanthanides and, by weight, one of the most expensive rare earths. It is a common bus, road, and jersey number with few strong cultural ties, though 1971 saw the first e-mail sent between two computers and the opening of Walt Disney World. In the ASCII character set, code 71 is the capital letter G.
Seventy-one is the twentieth prime and the lower member of the twin pair 71 and 73. It is an emirp, because its reversal 17 is also prime. It is the sum of three consecutive primes, 19 + 23 + 29. Its square, 5,041, is one more than 7 factorial, 5,040, a coincidence shared with only two other known pairs. In binary it is 1000111.
Nearby numbers
How to read this page
Because 71 is prime, the factor list stops at 1 and 71 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 71 in its prime factorisation inherits it from here.
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