28806221 has 4 divisors (see below), whose sum is σ = 29013600. Its totient is φ = 28598844.

The previous prime is 28806209. The next prime is 28806233. The reversal of 28806221 is 12260882.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12260882 = 2 ⋅6130441.

It is an interprime number because it is at equal distance from previous prime (28806209) and next prime (28806233).

It is a cyclic number.

It is not a de Polignac number, because 28806221 - 2⁶ = 28806157 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 (28806821) 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, 103481 + ... + 103758.

It is an arithmetic number, because the mean of its divisors is an integer number (7253400).

Almost surely, 2^28806221 is an apocalyptic number.

It is an amenable number.

28806221 is a deficient number, since it is larger than the sum of its proper divisors (207379).

28806221 is a wasteful number, since it uses less digits than its factorization.

28806221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 207378.

The product of its (nonzero) digits is 3072, while the sum is 29.

The square root of 28806221 is about 5367.1427221567. The cubic root of 28806221 is about 306.5458417897.

The spelling of 28806221 in words is "twenty-eight million, eight hundred six thousand, two hundred twenty-one".