28221428 has 18 divisors (see below), whose sum is σ = 52465686. Its totient is φ = 13280128.

The previous prime is 28221421. The next prime is 28221451. The reversal of 28221428 is 82412282.

It can be written as a sum of positive squares in 3 ways, for example, as 7171684 + 21049744 = 2678^2 + 4588^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 28221428.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28221421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 11051 + ... + 13362.

Almost surely, 2^28221428 is an apocalyptic number.

It is an amenable number.

28221428 is a deficient number, since it is larger than the sum of its proper divisors (24244258).

28221428 is a wasteful number, since it uses less digits than its factorization.

28221428 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24451 (or 24432 counting only the distinct ones).

The product of its digits is 4096, while the sum is 29.

The square root of 28221428 is about 5312.3843987422. The cubic root of 28221428 is about 304.4572556734.

The spelling of 28221428 in words is "twenty-eight million, two hundred twenty-one thousand, four hundred twenty-eight".