991138911 has 16 divisors (see below), whose sum is σ = 1520448000. Its totient is φ = 562562208.

The previous prime is 991138901. The next prime is 991138921. The reversal of 991138911 is 119831199.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (991138901) and next prime (991138921).

It is not a de Polignac number, because 991138911 - 2⁹ = 991138399 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991138901) 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 in 15 ways as a sum of consecutive naturals, for example, 155251 + ... + 161508.

It is an arithmetic number, because the mean of its divisors is an integer number (95028000).

Almost surely, 2^991138911 is an apocalyptic number.

991138911 is a deficient number, since it is larger than the sum of its proper divisors (529309089).

991138911 is a wasteful number, since it uses less digits than its factorization.

991138911 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 316918.

The product of its digits is 17496, while the sum is 42.

The square root of 991138911 is about 31482.3587267536. The cubic root of 991138911 is about 997.0375361409.

The spelling of 991138911 in words is "nine hundred ninety-one million, one hundred thirty-eight thousand, nine hundred eleven".