991931631 has 16 divisors (see below), whose sum is σ = 1405164000. Its totient is φ = 621226368.

The previous prime is 991931621. The next prime is 991931653. The reversal of 991931631 is 136139199.

It is not a de Polignac number, because 991931631 - 2¹⁵ = 991898863 is a prime.

It is a super-2 number, since 2×991931631² = 1967856721156640322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991931621) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 150856 + ... + 157293.

It is an arithmetic number, because the mean of its divisors is an integer number (87822750).

Almost surely, 2^991931631 is an apocalyptic number.

991931631 is a deficient number, since it is larger than the sum of its proper divisors (413232369).

991931631 is a wasteful number, since it uses less digits than its factorization.

991931631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 308218.

The product of its digits is 39366, while the sum is 42.

The square root of 991931631 is about 31494.9461183854. The cubic root of 991931631 is about 997.3032778937.

The spelling of 991931631 in words is "nine hundred ninety-one million, nine hundred thirty-one thousand, six hundred thirty-one".