28390681 has 16 divisors (see below), whose sum is σ = 32587200. Its totient is φ = 24494400.

The previous prime is 28390673. The next prime is 28390721. The reversal of 28390681 is 18609382.

It is a cyclic number.

It is not a de Polignac number, because 28390681 - 2³ = 28390673 is a prime.

It is a super-2 number, since 2×28390681² = 1612061535287522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28390681.

It is not an unprimeable number, because it can be changed into a prime (28390601) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18730 + ... + 20188.

It is an arithmetic number, because the mean of its divisors is an integer number (2036700).

Almost surely, 2^28390681 is an apocalyptic number.

It is an amenable number.

28390681 is a deficient number, since it is larger than the sum of its proper divisors (4196519).

28390681 is a wasteful number, since it uses less digits than its factorization.

28390681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1560.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 28390681 is about 5328.2906264580. The cubic root of 28390681 is about 305.0646857337.

The spelling of 28390681 in words is "twenty-eight million, three hundred ninety thousand, six hundred eighty-one".