999991031 has 8 divisors (see below), whose sum is σ = 1081538640. Its totient is φ = 919104192.

The previous prime is 999991009. The next prime is 999991037. The reversal of 999991031 is 130199999.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 999991031 - 2²² = 995796727 is a prime.

It is a super-2 number, since 2×999991031² = 1999964124160885922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999991037) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 162041 + ... + 168098.

It is an arithmetic number, because the mean of its divisors is an integer number (135192330).

Almost surely, 2^999991031 is an apocalyptic number.

999991031 is a deficient number, since it is larger than the sum of its proper divisors (81547609).

999991031 is a wasteful number, since it uses less digits than its factorization.

999991031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 330385.

The product of its (nonzero) digits is 177147, while the sum is 50.

The square root of 999991031 is about 31622.6347890241. The cubic root of 999991031 is about 999.9970103244.

The spelling of 999991031 in words is "nine hundred ninety-nine million, nine hundred ninety-one thousand, thirty-one".