28391931 has 8 divisors (see below), whose sum is σ = 42062160. Its totient is φ = 18927936.

The previous prime is 28391929. The next prime is 28391953. The reversal of 28391931 is 13919382.

It is not a de Polignac number, because 28391931 - 2¹ = 28391929 is a prime.

It is a super-2 number, since 2×28391931² = 1612203491817522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (28391971) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 525750 + ... + 525803.

It is an arithmetic number, because the mean of its divisors is an integer number (5257770).

Almost surely, 2^28391931 is an apocalyptic number.

28391931 is a deficient number, since it is larger than the sum of its proper divisors (13670229).

28391931 is a wasteful number, since it uses less digits than its factorization.

28391931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1051562 (or 1051556 counting only the distinct ones).

The product of its digits is 11664, while the sum is 36.

The square root of 28391931 is about 5328.4079235734. The cubic root of 28391931 is about 305.0691628514.

The spelling of 28391931 in words is "twenty-eight million, three hundred ninety-one thousand, nine hundred thirty-one".