28193921 has 4 divisors (see below), whose sum is σ = 32221632. Its totient is φ = 24166212.

The previous prime is 28193857. The next prime is 28193927. The reversal of 28193921 is 12939182.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 28193921 - 2⁶ = 28193857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28193927) 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, 2013845 + ... + 2013858.

It is an arithmetic number, because the mean of its divisors is an integer number (8055408).

Almost surely, 2^28193921 is an apocalyptic number.

It is an amenable number.

28193921 is a deficient number, since it is larger than the sum of its proper divisors (4027711).

28193921 is an equidigital number, since it uses as much as digits as its factorization.

28193921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4027710.

The product of its digits is 7776, while the sum is 35.

The square root of 28193921 is about 5309.7948171281. The cubic root of 28193921 is about 304.3583068875.

The spelling of 28193921 in words is "twenty-eight million, one hundred ninety-three thousand, nine hundred twenty-one".