197
This number is a prime.
The only three-digit prime repfigit number. [Trotter]
197 and 2197 * 197# - 1 are primes. [Boland]
The first three digits of the prime 197 * 197! + 1 are 197. [Luhn]
Surrey and England batsman Jack Hobbs scored a record 197 centuries.
The sum of the first dozen primes. [Brod]
The smallest prime number that is the sum of 7 consecutive prime numbers (17+19+23+29+31+37+41). [Schuler]
197 is the sum of digits of all two-digit primes. [Gallardo]
The smallest multidigit prime p that makes 10^p-9 prime. Note that the next prime (199) has the same property. They are twin primes! [Gallardo]
This prime is the smallest number to be the sum of repdigits of its digits: 111 + 9 + 77 = 197. [Post]
The sum of the squares of all the four composite digits (4^2 + 6^2 + 8^2 + 9^2). [Silva]
The digits contained in two-digit primes under 100, up to
97, sum to 100+97. [Silva]
If A=1, B=2, C=3, … , Z=26 then 'A PRIME QUADRUPLET' is one of four primes in a prime quadruplet. [Homewood]
19 x 7 + (1 x 9 x 7) + 1 = 197. [Homewood]
A self-referential (or auto-descriptive) sentence due to
Lee Sallows consists of a prime number of letters: "This
sentence contains one hundred and ninety-seven
letters: four a’s, one b, three c’s, five d’s, thirty-four
e’s, seven f’s, one g, six h’s, twelve i’s, three l’s,
twenty-six n’s, ten o’s, ten r’s, twenty-nine s’s, nineteen
t’s, six u’s, seven v’s, four w’s, four x’s, five y’s, and
one z." [Beedassy]
|8*k^2 + 8*k − 197| generates only primes for k = 0 to 30. [Yosei]
197 is a Russian Doll prime as 197, 97 and 7 are primes. [Buchanon]