28128381 has 16 divisors (see below), whose sum is σ = 38324928. Its totient is φ = 18345600.

The previous prime is 28128367. The next prime is 28128383. The reversal of 28128381 is 18382182.

It is not a de Polignac number, because 28128381 - 2⁵ = 28128349 is a prime.

It is a super-2 number, since 2×28128381² = 1582411635362322, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28128383) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 51150 + ... + 51696.

It is an arithmetic number, because the mean of its divisors is an integer number (2395308).

Almost surely, 2^28128381 is an apocalyptic number.

It is an amenable number.

28128381 is a deficient number, since it is larger than the sum of its proper divisors (10196547).

28128381 is a wasteful number, since it uses less digits than its factorization.

28128381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 892.

The product of its digits is 6144, while the sum is 33.

The square root of 28128381 is about 5303.6196130567. The cubic root of 28128381 is about 304.1222853200.

The spelling of 28128381 in words is "twenty-eight million, one hundred twenty-eight thousand, three hundred eighty-one".