28216681 has 8 divisors (see below), whose sum is σ = 29979720. Its totient is φ = 26506368.

The previous prime is 28216679. The next prime is 28216687. The reversal of 28216681 is 18661282.

It can be written as a sum of positive squares in 4 ways, for example, as 9511056 + 18705625 = 3084^2 + 4325^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 28216681 - 2¹ = 28216679 is a prime.

It is a super-2 number, since 2×28216681² = 1592362173311522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28216687) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12076 + ... + 14221.

It is an arithmetic number, because the mean of its divisors is an integer number (3747465).

Almost surely, 2^28216681 is an apocalyptic number.

It is an amenable number.

28216681 is a deficient number, since it is larger than the sum of its proper divisors (1763039).

28216681 is a wasteful number, since it uses less digits than its factorization.

28216681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26363.

The product of its digits is 9216, while the sum is 34.

The square root of 28216681 is about 5311.9375937599. The cubic root of 28216681 is about 304.4401842524.

The spelling of 28216681 in words is "twenty-eight million, two hundred sixteen thousand, six hundred eighty-one".