28875221 has 4 divisors (see below), whose sum is σ = 28890444. Its totient is φ = 28860000.

The previous prime is 28875169. The next prime is 28875227. The reversal of 28875221 is 12257882.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7623121 + 21252100 = 2761^2 + 4610^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28875221 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 (28875227) 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, 4280 + ... + 8721.

It is an arithmetic number, because the mean of its divisors is an integer number (7222611).

Almost surely, 2^28875221 is an apocalyptic number.

It is an amenable number.

28875221 is a deficient number, since it is larger than the sum of its proper divisors (15223).

28875221 is a wasteful number, since it uses less digits than its factorization.

28875221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15222.

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

The square root of 28875221 is about 5373.5668787129. The cubic root of 28875221 is about 306.7904046709.

The spelling of 28875221 in words is "twenty-eight million, eight hundred seventy-five thousand, two hundred twenty-one".