191591381 has 2 divisors, whose sum is σ = 191591382. Its totient is φ = 191591380.

The previous prime is 191591333. The next prime is 191591417. The reversal of 191591381 is 183195191.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 120340900 + 71250481 = 10970^2 + 8441^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-191591381 is a prime.

It is a super-2 number, since 2×191591381² = 73414514546974322, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (191596381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95795690 + 95795691.

It is an arithmetic number, because the mean of its divisors is an integer number (95795691).

Almost surely, 2^191591381 is an apocalyptic number.

It is an amenable number.

191591381 is a deficient number, since it is larger than the sum of its proper divisors (1).

191591381 is an equidigital number, since it uses as much as digits as its factorization.

191591381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9720, while the sum is 38.

The square root of 191591381 is about 13841.6538390468. The cubic root of 191591381 is about 576.4902801035.

The spelling of 191591381 in words is "one hundred ninety-one million, five hundred ninety-one thousand, three hundred eighty-one".