Number reference
197 explained.
197: one hundred ninety-seven, prime; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- one hundred ninety-seven
- Classification
- prime
- Factors
- 1, 197
- Prime factorization
- 197
- Square root
- 14.035669
- Cube root
- 5.818648
- Binary
- 11000101
- Octal
- 305
- Hexadecimal
- C5
- Roman numeral
- CXCVII
- Digit sum
- 17
- Digital root
- 8
What makes 197 notable
- Prime. 197 is prime: it has exactly two divisors, 1 and itself, so it cannot be split into equal whole-number groups any other way.
197 in everyday use
One hundred ninety-seven is the sum of the first twelve primes: 2 + 3 + 5 + 7 + 11 + 13 + 17 + 19 + 23 + 29 + 31 + 37. Sums of consecutive primes that are themselves prime are catalogued for their own sake, and 197 is one of the earliest large examples. It is also the third member of the prime quadruplet 191, 193, 197, 199, so it lives in one of the densest prime clusters found among three-digit numbers.
As a Pythagorean prime it can be written as 14² + 1², one more than a perfect square, a pattern shared with 5, 17, 37, and 101. Its digit sum is 17, which is prime. Reversed it becomes 791, which is 7 × 113, so 197 is not an emirp. It is the 45th prime, and it lies four short of 201, which is 3 × 67, and two short of 199, the last prime before 200.
Nearby numbers
How to read this page
Because 197 is prime, the factor list stops at 1 and 197 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 197 in its prime factorisation inherits it from here.
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