28705639 has 16 divisors (see below), whose sum is σ = 31477248. Its totient is φ = 26070912.

The previous prime is 28705631. The next prime is 28705657. The reversal of 28705639 is 93650782.

It is a cyclic number.

It is not a de Polignac number, because 28705639 - 2³ = 28705631 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 (28705631) 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 15 ways as a sum of consecutive naturals, for example, 78034 + ... + 78400.

It is an arithmetic number, because the mean of its divisors is an integer number (1967328).

Almost surely, 2^28705639 is an apocalyptic number.

28705639 is a deficient number, since it is larger than the sum of its proper divisors (2771609).

28705639 is a wasteful number, since it uses less digits than its factorization.

28705639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 534.

The product of its (nonzero) digits is 90720, while the sum is 40.

The square root of 28705639 is about 5357.7643658526. The cubic root of 28705639 is about 306.1886394350.

The spelling of 28705639 in words is "twenty-eight million, seven hundred five thousand, six hundred thirty-nine".