191819081 has 2 divisors, whose sum is σ = 191819082. Its totient is φ = 191819080.

The previous prime is 191819071. The next prime is 191819083. The reversal of 191819081 is 180918191.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 106090000 + 85729081 = 10300^2 + 9259^2 .

It is an emirp because it is prime and its reverse (180918191) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 191819081 - 2¹⁰ = 191818057 is a prime.

It is a super-2 number, since 2×191819081² = 73589119671369122, which contains 22 as substring.

Together with 191819083, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (191819083) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95909540 + 95909541.

It is an arithmetic number, because the mean of its divisors is an integer number (95909541).

Almost surely, 2^191819081 is an apocalyptic number.

It is an amenable number.

191819081 is a deficient number, since it is larger than the sum of its proper divisors (1).

191819081 is an equidigital number, since it uses as much as digits as its factorization.

191819081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 38.

The square root of 191819081 is about 13849.8765698471. The cubic root of 191819081 is about 576.7185695466.

The spelling of 191819081 in words is "one hundred ninety-one million, eight hundred nineteen thousand, eighty-one".