28217639 has 4 divisors (see below), whose sum is σ = 28604256. Its totient is φ = 27831024.

The previous prime is 28217627. The next prime is 28217659. The reversal of 28217639 is 93671282.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 28217639 - 2⁸ = 28217383 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 (28217659) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 193199 + ... + 193344.

It is an arithmetic number, because the mean of its divisors is an integer number (7151064).

Almost surely, 2^28217639 is an apocalyptic number.

28217639 is a deficient number, since it is larger than the sum of its proper divisors (386617).

28217639 is an equidigital number, since it uses as much as digits as its factorization.

28217639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 386616.

The product of its digits is 36288, while the sum is 38.

The square root of 28217639 is about 5312.0277672467. The cubic root of 28217639 is about 304.4436296186.

The spelling of 28217639 in words is "twenty-eight million, two hundred seventeen thousand, six hundred thirty-nine".