181
This number is a prime.
181 is the 9th palindromic prime number. Note that 9 divides 18 and 81, whose sum of digits are both 9.
There are 181 digits in 111!. [De Geest]
The 181st prime is congruent to 1 (mod 181). [Haga]
The prime value of x in the equation x2 = 2(3 * 5) - 7.
181 * 10181 + (10181 - 1) is prime. [Luhn]
The sum of the first 181 primes minus 181 is prime. [Gevisier]
The sum of the digits of the first 23 primes (2, ..., 83). [Trotter]
The 181-digit palindromic number made up of all 7's except for the center nut being 181 (7777...7718177...77777) is a palindromic prime with a palindromic prime decimal length. [Fougeron]
The first occurrence of two consecutive primes which are
both nontrivial (more than one digit) palindromes: 181,
191. [Murthy]
The smallest palindromic prime that remains prime through four iterations of the function f(x) = 2x + 5. [Russo]
The smaller of the first occurrence of two successive primes using no prime digits (181, 191). [Murthy]
The surface area of a pair Boeing 757 wings in square meters.
181 pennies currently minted in the U.S. weigh within a penny of a pound.
181 is the smallest odd prime (and fifth in all) exponent of 2 dissecting the interval between successive primes, i.e., 2^181 ± 165 are both prime with no intervening primes. [King]
181 = 92 + 102, i.e., the sum of two consecutive squares. [Mizuki]
No ship of the United States Navy has ever been named USS Haynes. A fictitious USS Haynes (DE-181) was the setting for the surface half of the movie The Enemy Below; her part was played by USS Whitehurst (DE-634). [Haga]
The smaller prime in the first multidigit "Gridgeman pair." A Gridgeman pair is two palindromic primes, which differ only in that their middle digits are x and x + 1 respectively. These are named in honor of Norman T. Gridgeman (1912-1995) who conjectured that there are an infinite number of primes in this form. [King]
The smallest palindromic prime number whose sum of digits
is composite. Note that 181 is also the smallest such that
at least one of the digits is composite. [Capelle]
181^2 = 105^3 - 104^3, i.e., a solution to the Diophantine
equation z^2 = x^3 - y^3. [Mizuki]
It is conjectured that there is always a prime between
xa and yb for all
integers x, y, a, b > 1,
except for the following
ten pairs: (23,32),
(52,33),
(25,62),
(112,53),
(37,133),
(55,562),
(1812,215),
(433,2822),
(463,3122), and
(224342,555). [Redmond and
Sun]
The smallest palindromic prime resulting from the sum of three consecutive emirps (37, 71, 73). [Silva]
The smallest prime which is a d-digit palindrome base 10 as
well as a d-digit palindrome for some base b different from
10. [Post]
Every natural number greater than 181 can be written as sum
of cubes of the first two primes. [Capelle]
181 candidates were nominated for the Nobel Peace Prize the
year Al Gore won it. [Francis]
The smallest prime decimal Goedelization of a theorem from
propositional calculus, symbolizing "A is logically
equivalent to A." [Post]
Only number n such that prime(n) = 6n + 1. [Firoozbakht]
The sum of strobogrammatic numbers less than or equal to 181 equals 666.
Can you find another strobogrammatic prime of the form
(5n^2+5n+2)/2? [Honaker]
"Cosmos: A Spacetime Odyssey" premiered in 181 countries.
The smallest multidigit palindromic prime that is equal to
the sum of the digits of 181^n for n = 16, 18, 19 and 20. [Gupta]
There are at least 181 Las Bolas Grandes ('The Great Stone Balls' in Spanish) of Costa Rico that survive whole. [Lothrop]
The complex vitamin B12 molecule contains a total of 181 atoms. [Newmark]
List all the whole numbers less than 1000, that is 0 - 999.
The number of whole numbers in the list containing the
digit 0 is 181. [Green]
181 is a palindromic Pythagorean prime, equal to the sum of
the squares of 10 and 9. [Green]
Sri Lanka was ruled by 181 monarchs from the Anuradhapura
to Kandy periods.
181 equals the sum of the squares of three consecutive
composite digits: 6^2+8^2+9^2. [Silva]
The number of days in a non-leap year from January 1 to June 30. [Gupta]
The smallest prime that can be represented as sum of
squares of successive composite numbers, in two ways, i.e.,
6^2+8^2+9^2 and 9^2+10^2. [Loungrides]
1000 is the 181st positive integer that contains at least
one pair of equal digits adjacent to each other. [Gaydos]
The smallest palindromic prime expressed as 2n^2+2n+1. [Silva]
Bobby Fischer was believed to have an I.Q. of 181. [Maven]
Martha Graham created 181 ballets. [Baumgardner]
The palindromic ZIP Code of Andover MA is 181 with a zero on each end. [Schvanger]
Is 181 the only prime palindromic prime that produces another when added to its sum of digits? [Gaydos]