28331388 has 18 divisors (see below), whose sum is σ = 71615544. Its totient is φ = 9443784.

The previous prime is 28331371. The next prime is 28331393. The reversal of 28331388 is 88313382.

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 786983 = 28331388 / (2 + 8 + 3 + 3 + 1 + 3 + 8 + 8).

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 5 ways as a sum of consecutive naturals, for example, 393456 + ... + 393527.

Almost surely, 2^28331388 is an apocalyptic number.

It is an amenable number.

28331388 is an abundant number, since it is smaller than the sum of its proper divisors (43284156).

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

28331388 is a wasteful number, since it uses less digits than its factorization.

28331388 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 786993 (or 786988 counting only the distinct ones).

The product of its digits is 27648, while the sum is 36.

The square root of 28331388 is about 5322.7237388390. The cubic root of 28331388 is about 304.8521652093.

The spelling of 28331388 in words is "twenty-eight million, three hundred thirty-one thousand, three hundred eighty-eight".