28221857 has 4 divisors (see below), whose sum is σ = 28303536. Its totient is φ = 28140180.

The previous prime is 28221847. The next prime is 28221871. The reversal of 28221857 is 75812282.

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 a cyclic number.

It is not a de Polignac number, because 28221857 - 2⁶ = 28221793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28221827) 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, 40319 + ... + 41012.

It is an arithmetic number, because the mean of its divisors is an integer number (7075884).

Almost surely, 2^28221857 is an apocalyptic number.

It is an amenable number.

28221857 is a deficient number, since it is larger than the sum of its proper divisors (81679).

28221857 is an equidigital number, since it uses as much as digits as its factorization.

28221857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81678.

The product of its digits is 17920, while the sum is 35.

The square root of 28221857 is about 5312.4247759380. The cubic root of 28221857 is about 304.4587983723.

The spelling of 28221857 in words is "twenty-eight million, two hundred twenty-one thousand, eight hundred fifty-seven".