28691638 has 8 divisors (see below), whose sum is σ = 43263360. Its totient is φ = 14270520.

The previous prime is 28691633. The next prime is 28691651. The reversal of 28691638 is 83619682.

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

It is a super-2 number, since 2×28691638² = 1646420182246088, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 28691594 and 28691603.

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 3 ways as a sum of consecutive naturals, for example, 37173 + ... + 37936.

It is an arithmetic number, because the mean of its divisors is an integer number (5407920).

Almost surely, 2^28691638 is an apocalyptic number.

28691638 is a deficient number, since it is larger than the sum of its proper divisors (14571722).

28691638 is a wasteful number, since it uses less digits than its factorization.

28691638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75302.

The product of its digits is 124416, while the sum is 43.

The square root of 28691638 is about 5356.4575980773. The cubic root of 28691638 is about 306.1388507935.

The spelling of 28691638 in words is "twenty-eight million, six hundred ninety-one thousand, six hundred thirty-eight".