28528981 has 4 divisors (see below), whose sum is σ = 30723532. Its totient is φ = 26334432.

The previous prime is 28528979. The next prime is 28529027. The reversal of 28528981 is 18982582.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18982582 = 2 ⋅9491291.

It can be written as a sum of positive squares in 2 ways, for example, as 1134225 + 27394756 = 1065^2 + 5234^2 .

It is a cyclic number.

It is not a de Polignac number, because 28528981 - 2¹ = 28528979 is a prime.

It is a super-2 number, since 2×28528981² = 1627805513796722, 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 (28528781) 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 3 ways as a sum of consecutive naturals, for example, 1097256 + ... + 1097281.

It is an arithmetic number, because the mean of its divisors is an integer number (7680883).

Almost surely, 2^28528981 is an apocalyptic number.

It is an amenable number.

28528981 is a deficient number, since it is larger than the sum of its proper divisors (2194551).

28528981 is a wasteful number, since it uses less digits than its factorization.

28528981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2194550.

The product of its digits is 92160, while the sum is 43.

The square root of 28528981 is about 5341.2527556745. The cubic root of 28528981 is about 305.5592391304.

The spelling of 28528981 in words is "twenty-eight million, five hundred twenty-eight thousand, nine hundred eighty-one".