30991728 has 20 divisors (see below), whose sum is σ = 80062088. Its totient is φ = 10330560.

The previous prime is 30991703. The next prime is 30991733. The reversal of 30991728 is 82719903.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 322783 + ... + 322878.

Almost surely, 2^30991728 is an apocalyptic number.

It is an amenable number.

30991728 is an abundant number, since it is smaller than the sum of its proper divisors (49070360).

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

30991728 is a wasteful number, since it uses less digits than its factorization.

30991728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 645672 (or 645666 counting only the distinct ones).

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 30991728 is about 5567.0214657391. The cubic root of 30991728 is about 314.1101213548.

The spelling of 30991728 in words is "thirty million, nine hundred ninety-one thousand, seven hundred twenty-eight".