28331921 has 4 divisors (see below), whose sum is σ = 28411200. Its totient is φ = 28252644.

The previous prime is 28331893. The next prime is 28331939. The reversal of 28331921 is 12913382.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12913382 = 2 ⋅6456691.

It is a cyclic number.

It is not a de Polignac number, because 28331921 - 2¹⁴ = 28315537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28331951) 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, 39101 + ... + 39818.

It is an arithmetic number, because the mean of its divisors is an integer number (7102800).

Almost surely, 2^28331921 is an apocalyptic number.

It is an amenable number.

28331921 is a deficient number, since it is larger than the sum of its proper divisors (79279).

28331921 is an equidigital number, since it uses as much as digits as its factorization.

28331921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79278.

The product of its digits is 2592, while the sum is 29.

The square root of 28331921 is about 5322.7738069544. The cubic root of 28331921 is about 304.8540769310.

The spelling of 28331921 in words is "twenty-eight million, three hundred thirty-one thousand, nine hundred twenty-one".