28941221 has 4 divisors (see below), whose sum is σ = 29197452. Its totient is φ = 28684992.

The previous prime is 28941181. The next prime is 28941229. The reversal of 28941221 is 12214982.

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 15880225 + 13060996 = 3985^2 + 3614^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28941221 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 (28941229) 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, 127946 + ... + 128171.

It is an arithmetic number, because the mean of its divisors is an integer number (7299363).

Almost surely, 2^28941221 is an apocalyptic number.

It is an amenable number.

28941221 is a deficient number, since it is larger than the sum of its proper divisors (256231).

28941221 is a wasteful number, since it uses less digits than its factorization.

28941221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 256230.

The product of its digits is 2304, while the sum is 29.

The square root of 28941221 is about 5379.7045457906. The cubic root of 28941221 is about 307.0239700892.

The spelling of 28941221 in words is "twenty-eight million, nine hundred forty-one thousand, two hundred twenty-one".