28688981 has 8 divisors (see below), whose sum is σ = 30902784. Its totient is φ = 26555760.

The previous prime is 28688923. The next prime is 28688987. The reversal of 28688981 is 18988682.

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

It is a cyclic number.

It is not a de Polignac number, because 28688981 - 2¹⁸ = 28426837 is a prime.

It is a super-2 number, since 2×28688981² = 1646115261636722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28688987) 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 7 ways as a sum of consecutive naturals, for example, 19406 + ... + 20831.

It is an arithmetic number, because the mean of its divisors is an integer number (3862848).

Almost surely, 2^28688981 is an apocalyptic number.

It is an amenable number.

28688981 is a deficient number, since it is larger than the sum of its proper divisors (2213803).

28688981 is a wasteful number, since it uses less digits than its factorization.

28688981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40291.

The product of its digits is 442368, while the sum is 50.

The square root of 28688981 is about 5356.2095739431. The cubic root of 28688981 is about 306.1294004671.

The spelling of 28688981 in words is "twenty-eight million, six hundred eighty-eight thousand, nine hundred eighty-one".