28345681 has 32 divisors (see below), whose sum is σ = 37594368. Its totient is φ = 20736000.

The previous prime is 28345679. The next prime is 28345693. The reversal of 28345681 is 18654382.

It is a happy number.

It is a 3-Lehmer number, since φ(28345681) divides (28345681-1)³.

It is a cyclic number.

It is not a de Polignac number, because 28345681 - 2¹ = 28345679 is a prime.

It is a super-2 number, since 2×28345681² = 1606955262707522, which contains 22 as substring.

It is a Smith number, since the sum of its digits (37) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 28345681.

It is not an unprimeable number, because it can be changed into a prime (28345601) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 112806 + ... + 113056.

It is an arithmetic number, because the mean of its divisors is an integer number (1174824).

Almost surely, 2^28345681 is an apocalyptic number.

It is an amenable number.

28345681 is a deficient number, since it is larger than the sum of its proper divisors (9248687).

28345681 is a wasteful number, since it uses less digits than its factorization.

28345681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 361.

The product of its digits is 46080, while the sum is 37.

The square root of 28345681 is about 5324.0662092051. The cubic root of 28345681 is about 304.9034218988.

It can be divided in two parts, 2834 and 5681, that added together give a triangular number (8515 = T₁₃₀).

The spelling of 28345681 in words is "twenty-eight million, three hundred forty-five thousand, six hundred eighty-one".