28615681 has 4 divisors (see below), whose sum is σ = 28700932. Its totient is φ = 28530432.

The previous prime is 28615673. The next prime is 28615693. The reversal of 28615681 is 18651682.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6713281 + 21902400 = 2591^2 + 4680^2 .

It is a cyclic number.

It is not a de Polignac number, because 28615681 - 2³ = 28615673 is a prime.

It is a super-2 number, since 2×28615681² = 1637714398187522, 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 28615681.

It is not an unprimeable number, because it can be changed into a prime (28645681) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 42120 + ... + 42793.

It is an arithmetic number, because the mean of its divisors is an integer number (7175233).

Almost surely, 2^28615681 is an apocalyptic number.

It is an amenable number.

28615681 is a deficient number, since it is larger than the sum of its proper divisors (85251).

28615681 is an equidigital number, since it uses as much as digits as its factorization.

28615681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 85250.

The product of its digits is 23040, while the sum is 37.

The square root of 28615681 is about 5349.3626723190. The cubic root of 28615681 is about 305.8684591330.

The spelling of 28615681 in words is "twenty-eight million, six hundred fifteen thousand, six hundred eighty-one".