28123681 has 4 divisors (see below), whose sum is σ = 28228500. Its totient is φ = 28018864.

The previous prime is 28123679. The next prime is 28123703. The reversal of 28123681 is 18632182.

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 5475600 + 22648081 = 2340^2 + 4759^2 .

It is a cyclic number.

It is not a de Polignac number, because 28123681 - 2¹ = 28123679 is a prime.

It is a super-2 number, since 2×28123681² = 1581882865979522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28123621) 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, 52006 + ... + 52543.

It is an arithmetic number, because the mean of its divisors is an integer number (7057125).

Almost surely, 2^28123681 is an apocalyptic number.

It is an amenable number.

28123681 is a deficient number, since it is larger than the sum of its proper divisors (104819).

28123681 is a wasteful number, since it uses less digits than its factorization.

28123681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 104818.

The product of its digits is 4608, while the sum is 31.

The square root of 28123681 is about 5303.1765009285. The cubic root of 28123681 is about 304.1053456751.

The spelling of 28123681 in words is "twenty-eight million, one hundred twenty-three thousand, six hundred eighty-one".