28633681 has 4 divisors (see below), whose sum is σ = 28704100. Its totient is φ = 28563264.

The previous prime is 28633679. The next prime is 28633687. The reversal of 28633681 is 18633682.

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 15673681 + 12960000 = 3959^2 + 3600^2 .

It is a cyclic number.

It is not a de Polignac number, because 28633681 - 2¹ = 28633679 is a prime.

It is a super-2 number, since 2×28633681² = 1639775375219522, which contains 22 as substring.

It is a Duffinian number.

28633681 is a modest number, since divided by 3681 gives 2863 as remainder.

It is a self number, because there is not a number n which added to its sum of digits gives 28633681.

It is not an unprimeable number, because it can be changed into a prime (28633687) 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, 34596 + ... + 35413.

It is an arithmetic number, because the mean of its divisors is an integer number (7176025).

Almost surely, 2^28633681 is an apocalyptic number.

It is an amenable number.

28633681 is a deficient number, since it is larger than the sum of its proper divisors (70419).

28633681 is an equidigital number, since it uses as much as digits as its factorization.

28633681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70418.

The product of its digits is 41472, while the sum is 37.

The square root of 28633681 is about 5351.0448512417. The cubic root of 28633681 is about 305.9325787355.

Subtracting from 28633681 its reverse (18633682), we obtain a palindrome (9999999).

The spelling of 28633681 in words is "twenty-eight million, six hundred thirty-three thousand, six hundred eighty-one".