115991381 has 4 divisors (see below), whose sum is σ = 126536064. Its totient is φ = 105446700.

The previous prime is 115991377. The next prime is 115991383. The reversal of 115991381 is 183199511.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 183199511 = 11 ⋅16654501.

It is a cyclic number.

It is not a de Polignac number, because 115991381 - 2² = 115991377 is a prime.

It is a super-2 number, since 2×115991381² = 26908000932574322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (115991383) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5272325 + ... + 5272346.

It is an arithmetic number, because the mean of its divisors is an integer number (31634016).

Almost surely, 2^115991381 is an apocalyptic number.

115991381 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

115991381 is a deficient number, since it is larger than the sum of its proper divisors (10544683).

115991381 is a wasteful number, since it uses less digits than its factorization.

115991381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10544682.

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

The square root of 115991381 is about 10769.9294798063. The cubic root of 115991381 is about 487.6878168271.

The spelling of 115991381 in words is "one hundred fifteen million, nine hundred ninety-one thousand, three hundred eighty-one".