991631808 has 140 divisors (see below), whose sum is σ = 2957471352. Its totient is φ = 328527360.

The previous prime is 991631791. The next prime is 991631827. The reversal of 991631808 is 808136199.

991631808 is a `hidden beast` number, since 9 + 9 + 1 + 631 + 8 + 0 + 8 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1020763 + ... + 1021733.

Almost surely, 2^991631808 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 991631808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1478735676).

991631808 is an abundant number, since it is smaller than the sum of its proper divisors (1965839544).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

991631808 is a wasteful number, since it uses less digits than its factorization.

991631808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1192 (or 1173 counting only the distinct ones).

The product of its (nonzero) digits is 93312, while the sum is 45.

The square root of 991631808 is about 31490.1858997371. The cubic root of 991631808 is about 997.2027855535.

The spelling of 991631808 in words is "nine hundred ninety-one million, six hundred thirty-one thousand, eight hundred eight".