9991028 has 6 divisors (see below), whose sum is σ = 17484306. Its totient is φ = 4995512.

The previous prime is 9991027. The next prime is 9991057. The reversal of 9991028 is 8201999.

9991028 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 5071504 + 4919524 = 2252^2 + 2218^2 .

It is a junction number, because it is equal to n+sod(n) for n = 9990982 and 9991000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9991027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1248875 + ... + 1248882.

It is an arithmetic number, because the mean of its divisors is an integer number (2914051).

Almost surely, 2^9991028 is an apocalyptic number.

It is an amenable number.

9991028 is a deficient number, since it is larger than the sum of its proper divisors (7493278).

9991028 is a wasteful number, since it uses less digits than its factorization.

9991028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2497761 (or 2497759 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 38.

The square root of 9991028 is about 3160.8587440757. The cubic root of 9991028 is about 215.3790177640.

The spelling of 9991028 in words is "nine million, nine hundred ninety-one thousand, twenty-eight".