28323991 has 4 divisors (see below), whose sum is σ = 28356952. Its totient is φ = 28291032.

The previous prime is 28323979. The next prime is 28324013. The reversal of 28323991 is 19932382.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19932382 = 2 ⋅9966191.

It is a cyclic number.

It is not a de Polignac number, because 28323991 - 2¹³ = 28315799 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28323991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28323961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15156 + ... + 16921.

It is an arithmetic number, because the mean of its divisors is an integer number (7089238).

Almost surely, 2^28323991 is an apocalyptic number.

28323991 is a deficient number, since it is larger than the sum of its proper divisors (32961).

28323991 is an equidigital number, since it uses as much as digits as its factorization.

28323991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32960.

The product of its digits is 23328, while the sum is 37.

The square root of 28323991 is about 5322.0288424622. The cubic root of 28323991 is about 304.8256317670.

The spelling of 28323991 in words is "twenty-eight million, three hundred twenty-three thousand, nine hundred ninety-one".