This number is a prime.
The sum of 2 + 3 + 4 + ... + 19 minus the sum of primes less than 19. [Trotter]
Iodine-131 is a radioactive isotope used in thyroid disease diagnosis and therapy. [Barnhart]
The sum of three two-digit primes (31 + 41 + 59) whose concatenation is the decimal expansion of π. [Silva]
(2! + 1) + (3! + 1) + (5! + 1) = 131. This is equivalent to 3 + 7 + 11^2. [La Haye]
The nematode Caenorhabditis elegans hermaphrodite has exactly 131 cells that are eliminated by programmed cell death (apoptosis). [Haga]
The smallest palindromic super-2 number, i.e., an integer n such that 2n^2 contains 2 consecutive 2s in its decimal representation. [De Geest]
The sum of the first 131 non-primes is prime. [Patterson]
131 = (1^0+3^0+1^0) + (1^1+3^1+1^1) + (1^2+3^2+1^2) + (1^3+3^3+1^3) + (1^4+3^4+1^4). Note that the summands are all primes. [Silva]
131 and the next prime after it are the first pair of consecutive primes where we can find another pair of consecutive primes by concatenating each term's end digits. [Silva]
The smallest prime number appearing after the concatenation of the two preceding prime numbers (113 and 127). [Capelle]
The smallest palindromic prime that yields another if the sum of digits of its consecutive digits is sandwiched between each of the corresponding consecutive digits (i.e., 131 becomes 14341). [Silva]
A prime Ulam number that is the sum of two consecutive Ulam numbers (62 + 69 = 131). Can you find a greater prime example?
The smallest palindromic prime using two distinct digits which when interchanged forms another palindromic prime (313). Note that in both cases a new palindromic prime with a prime number of digits is generated when each digit d is repeated d times: 13331; 3331333. [Beedassy]
The smallest Honaker prime, i.e., 131 = P32, and 1 + 3 + 1 = 3 + 2. Note that the latter sum of digits corresponds to the smallest prime with prime subscript (3 = P2) added to its very (prime) subscript. [Beedassy]
131 families of Coleoptera (beetles) have been described in North America. [Bartlett]
The smallest prime formed from overlapping an emirp pair (13 and 31).
A checking method is described to see if 131 is prime at the bottom of "Prime Factors" (a page from a Houghton Mifflin Harcourt website called Education Place).
The smallest prime equidistant between two consecutive emirps: 113, 149. [Beedassy]
The 1st prime after p(31) is 131. [Silva]
The smallest n-digit palindromic prime with central digit n, (n=3). [Loungrides]
The smallest palindromic prime that is the sum of three consecutive primes (41+43+47). [Silva]
The smallest prime of form p*q-(r+s), where p, q, r, s are four consecutive primes, i.e., (13, 11, 7, 5). [Loungrides]
The fifth prime whose sum of digits is 5. [Loungrides]
Daigoro's father cut off the heads of 131 lords for the Shogun. [Post]
Smallest Sophie German prime which is also an irregular prime.
The smallest palindromic prime with exactly three nonzero digits. [Buddenhagaen]
131 is the smallest pallindromic prime that remains so by inserting the following same digit d six times between its adjacent digits, one at a time, for d = 0, 1, 3, 4, 6, 9 (6 times): 10301 = prime 11311 = prime 13331 = prime 14341 = prime 16361 = prime 19391 = prime. [Rivera]
The sum of the first one hundred thirty one 131-digit primes is prime. Can you find a larger example like this? [Gaydos]
The restaurant "131" (www.one-thirtyone.com) is nestled in Hong Kong's Three Fathoms Cove. It is reminiscent of a luxury European country retreat in an atmosphere that is elegant and relaxed.
The Collatz trajectory length of 131000. [Gaydos]
The first three-digit term to occur in Van Eck's Sequence.
131 is the sum of three two-digit primes which appear as first digits of the decimal expansion of pi: 31+41+59. [Silva]
The smallest and possibly the only odd-digit palindromic prime that is partial sums of numbers (1+3+5+7+9...+31 = 131) whose divisors have only odd digits. Note that the primes with this property are 131, 199, 379, 519793, 113715733399, ... . [Sariyar]
131 can be written as the sum of three distinct prime-digit primes with distinct prime digits, i.e., 131 = 5 + 53 + 73.
131 is the smallest prime fully auto-insertable (into all of its internal positions), one at a time. Accordingly, the following two integers are primes: 1'131'31, 13'131'1 [Rivera]