28217989 has 4 divisors (see below), whose sum is σ = 28696320. Its totient is φ = 27739660.

The previous prime is 28217971. The next prime is 28217993. The reversal of 28217989 is 98971282.

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.

It is a cyclic number.

It is not a de Polignac number, because 28217989 - 2⁹ = 28217477 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 (28217999) 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, 239077 + ... + 239194.

It is an arithmetic number, because the mean of its divisors is an integer number (7174080).

Almost surely, 2^28217989 is an apocalyptic number.

It is an amenable number.

28217989 is a deficient number, since it is larger than the sum of its proper divisors (478331).

28217989 is an equidigital number, since it uses as much as digits as its factorization.

28217989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 478330.

The product of its digits is 145152, while the sum is 46.

The square root of 28217989 is about 5312.0607112494. The cubic root of 28217989 is about 304.4448883446. Note that the first 3 decimals are identical.

The spelling of 28217989 in words is "twenty-eight million, two hundred seventeen thousand, nine hundred eighty-nine".