28516221 has 12 divisors (see below), whose sum is σ = 41254720. Its totient is φ = 18981000.

The previous prime is 28516217. The next prime is 28516231. The reversal of 28516221 is 12261582.

It is a happy number.

It is not a de Polignac number, because 28516221 - 2² = 28516217 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 (28516231) 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 11 ways as a sum of consecutive naturals, for example, 4650 + ... + 8868.

Almost surely, 2^28516221 is an apocalyptic number.

It is an amenable number.

28516221 is a deficient number, since it is larger than the sum of its proper divisors (12738499).

28516221 is a wasteful number, since it uses less digits than its factorization.

28516221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4976 (or 4973 counting only the distinct ones).

The product of its digits is 1920, while the sum is 27.

The square root of 28516221 is about 5340.0581457508. The cubic root of 28516221 is about 305.5136770717.

It can be divided in two parts, 28516 and 221, that multiplied together give a palindrome (6302036).

The spelling of 28516221 in words is "twenty-eight million, five hundred sixteen thousand, two hundred twenty-one".