28681 has 8 divisors (see below), whose sum is σ = 31680. Its totient is φ = 25872.

The previous prime is 28669. The next prime is 28687. The reversal of 28681 is 18682.

28681 = T₃₈ + T₃₉ + ... + T₆₀.

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 28681 - 2⁵ = 28649 is a prime.

It is a super-2 number, since 2×28681² = 1645199522, which contains 22 as substring.

It is a pancake number, because a pancake can be divided into 28681 parts by 239 straight cuts.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (28687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 646 + ... + 688.

It is an arithmetic number, because the mean of its divisors is an integer number (3960).

2²⁸⁶⁸¹ is an apocalyptic number.

It is an amenable number.

28681 is a deficient number, since it is larger than the sum of its proper divisors (2999).

28681 is a wasteful number, since it uses less digits than its factorization.

28681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95.

The product of its digits is 768, while the sum is 25.

The square root of 28681 is about 169.3546574500. The cubic root of 28681 is about 30.6101010411.

Subtracting from 28681 its reverse (18682), we obtain a palindrome (9999).

The spelling of 28681 in words is "twenty-eight thousand, six hundred eighty-one".