28231291 has 4 divisors (see below), whose sum is σ = 30797784. Its totient is φ = 25664800.

The previous prime is 28231289. The next prime is 28231387. The reversal of 28231291 is 19213282.

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 28231291 - 2¹ = 28231289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28231261) 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, 1283230 + ... + 1283251.

It is an arithmetic number, because the mean of its divisors is an integer number (7699446).

Almost surely, 2^28231291 is an apocalyptic number.

28231291 is a deficient number, since it is larger than the sum of its proper divisors (2566493).

28231291 is a wasteful number, since it uses less digits than its factorization.

28231291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2566492.

The product of its digits is 1728, while the sum is 28.

The square root of 28231291 is about 5313.3126202022. The cubic root of 28231291 is about 304.4927194134.

Subtracting from 28231291 its reverse (19213282), we obtain a square (9018009 = 3003²).

It can be divided in two parts, 2823 and 1291, that added together give a palindrome (4114).

The spelling of 28231291 in words is "twenty-eight million, two hundred thirty-one thousand, two hundred ninety-one".