28870221 has 16 divisors (see below), whose sum is σ = 40337280. Its totient is φ = 18332160.

The previous prime is 28870217. The next prime is 28870229. The reversal of 28870221 is 12207882.

It is a happy number.

It is not a de Polignac number, because 28870221 - 2² = 28870217 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28870229) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18645 + ... + 20133.

It is an arithmetic number, because the mean of its divisors is an integer number (2521080).

Almost surely, 2^28870221 is an apocalyptic number.

It is an amenable number.

28870221 is a deficient number, since it is larger than the sum of its proper divisors (11467059).

28870221 is a wasteful number, since it uses less digits than its factorization.

28870221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1796.

The product of its (nonzero) digits is 3584, while the sum is 30.

The square root of 28870221 is about 5373.1016182462. The cubic root of 28870221 is about 306.7726958244.

The spelling of 28870221 in words is "twenty-eight million, eight hundred seventy thousand, two hundred twenty-one".