28221999 has 16 divisors (see below), whose sum is σ = 40908672. Its totient is φ = 17202528.

The previous prime is 28221971. The next prime is 28222021. The reversal of 28221999 is 99912282.

It is a happy number.

It is not a de Polignac number, because 28221999 - 2⁵ = 28221967 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 28221999.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28221929) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 792 + ... + 7554.

It is an arithmetic number, because the mean of its divisors is an integer number (2556792).

Almost surely, 2^28221999 is an apocalyptic number.

28221999 is a deficient number, since it is larger than the sum of its proper divisors (12686673).

28221999 is a wasteful number, since it uses less digits than its factorization.

28221999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6886.

The product of its digits is 46656, while the sum is 42.

The square root of 28221999 is about 5312.4381408163. The cubic root of 28221999 is about 304.4593090058.

The spelling of 28221999 in words is "twenty-eight million, two hundred twenty-one thousand, nine hundred ninety-nine".