28691639 has 8 divisors (see below), whose sum is σ = 28980000. Its totient is φ = 28405152.

The previous prime is 28691633. The next prime is 28691651. The reversal of 28691639 is 93619682.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28691639 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28691639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28691633) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 79742 + ... + 80100.

It is an arithmetic number, because the mean of its divisors is an integer number (3622500).

Almost surely, 2^28691639 is an apocalyptic number.

28691639 is a deficient number, since it is larger than the sum of its proper divisors (288361).

28691639 is a wasteful number, since it uses less digits than its factorization.

28691639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 937.

The product of its digits is 139968, while the sum is 44.

The square root of 28691639 is about 5356.4576914226. The cubic root of 28691639 is about 306.1388543502.

The spelling of 28691639 in words is "twenty-eight million, six hundred ninety-one thousand, six hundred thirty-nine".