28181989 has 12 divisors (see below), whose sum is σ = 31124128. Its totient is φ = 25498440.

The previous prime is 28181977. The next prime is 28182013. The reversal of 28181989 is 98918182.

It is not a de Polignac number, because 28181989 - 2⁵ = 28181957 is a prime.

It is a super-2 number, since 2×28181989² = 1588449007992242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28181089) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 33832 + ... + 34654.

Almost surely, 2^28181989 is an apocalyptic number.

It is an amenable number.

28181989 is a deficient number, since it is larger than the sum of its proper divisors (2942139).

28181989 is a wasteful number, since it uses less digits than its factorization.

28181989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1128 (or 1117 counting only the distinct ones).

The product of its digits is 82944, while the sum is 46.

The square root of 28181989 is about 5308.6711143185. The cubic root of 28181989 is about 304.3153648203.

The spelling of 28181989 in words is "twenty-eight million, one hundred eighty-one thousand, nine hundred eighty-nine".