28391691 has 24 divisors (see below), whose sum is σ = 40341504. Its totient is φ = 17742240.

The previous prime is 28391687. The next prime is 28391707. The reversal of 28391691 is 19619382.

It is not a de Polignac number, because 28391691 - 2² = 28391687 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28391791) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 127206 + ... + 127428.

It is an arithmetic number, because the mean of its divisors is an integer number (1680896).

Almost surely, 2^28391691 is an apocalyptic number.

28391691 is a deficient number, since it is larger than the sum of its proper divisors (11949813).

28391691 is a wasteful number, since it uses less digits than its factorization.

28391691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 331 (or 294 counting only the distinct ones).

The product of its digits is 23328, while the sum is 39.

The square root of 28391691 is about 5328.3854027275. The cubic root of 28391691 is about 305.0683032550.

The spelling of 28391691 in words is "twenty-eight million, three hundred ninety-one thousand, six hundred ninety-one".