28931421 has 4 divisors (see below), whose sum is σ = 38575232. Its totient is φ = 19287612.

The previous prime is 28931411. The next prime is 28931423. The reversal of 28931421 is 12413982.

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 28931421 - 2²² = 24737117 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28931423) 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, 4821901 + ... + 4821906.

It is an arithmetic number, because the mean of its divisors is an integer number (9643808).

Almost surely, 2^28931421 is an apocalyptic number.

It is an amenable number.

28931421 is a deficient number, since it is larger than the sum of its proper divisors (9643811).

28931421 is an equidigital number, since it uses as much as digits as its factorization.

28931421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9643810.

The product of its digits is 3456, while the sum is 30.

The square root of 28931421 is about 5378.7936379824. The cubic root of 28931421 is about 306.9893116277.

The spelling of 28931421 in words is "twenty-eight million, nine hundred thirty-one thousand, four hundred twenty-one".