28639221 has 32 divisors (see below), whose sum is σ = 42900480. Its totient is φ = 16879104.

The previous prime is 28639207. The next prime is 28639223. The reversal of 28639221 is 12293682.

It is a happy number.

It is not a de Polignac number, because 28639221 - 2⁶ = 28639157 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28639223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 128316 + ... + 128538.

It is an arithmetic number, because the mean of its divisors is an integer number (1340640).

Almost surely, 2^28639221 is an apocalyptic number.

It is an amenable number.

28639221 is a deficient number, since it is larger than the sum of its proper divisors (14261259).

28639221 is a wasteful number, since it uses less digits than its factorization.

28639221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 365.

The product of its digits is 10368, while the sum is 33.

The square root of 28639221 is about 5351.5624821168. The cubic root of 28639221 is about 305.9523079161.

The spelling of 28639221 in words is "twenty-eight million, six hundred thirty-nine thousand, two hundred twenty-one".