991018388 has 12 divisors (see below), whose sum is σ = 1809685920. Its totient is φ = 473965272.

The previous prime is 991018367. The next prime is 991018429. The reversal of 991018388 is 883810199.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5385878 + ... + 5386061.

It is an arithmetic number, because the mean of its divisors is an integer number (150807160).

Almost surely, 2^991018388 is an apocalyptic number.

It is an amenable number.

991018388 is a deficient number, since it is larger than the sum of its proper divisors (818667532).

991018388 is a wasteful number, since it uses less digits than its factorization.

991018388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10771966 (or 10771964 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 47.

The square root of 991018388 is about 31480.4445330748. Note that the first 3 decimals coincide. The cubic root of 991018388 is about 996.9971210774.

The spelling of 991018388 in words is "nine hundred ninety-one million, eighteen thousand, three hundred eighty-eight".