28691 has 4 divisors (see below), whose sum is σ = 30912. Its totient is φ = 26472.

The previous prime is 28687. The next prime is 28697. The reversal of 28691 is 19682.

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

It is a cyclic number.

It is not a de Polignac number, because 28691 - 2² = 28687 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 28691.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 28691.

It is not an unprimeable number, because it can be changed into a prime (28697) 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, 1091 + ... + 1116.

It is an arithmetic number, because the mean of its divisors is an integer number (7728).

2²⁸⁶⁹¹ is an apocalyptic number.

28691 is a deficient number, since it is larger than the sum of its proper divisors (2221).

28691 is a wasteful number, since it uses less digits than its factorization.

28691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2220.

The product of its digits is 864, while the sum is 26.

The square root of 28691 is about 169.3841787181. The cubic root of 28691 is about 30.6136581630.

Subtracting from 28691 its reverse (19682), we obtain a palindrome (9009).

The spelling of 28691 in words is "twenty-eight thousand, six hundred ninety-one".