28911381 has 4 divisors (see below), whose sum is σ = 38548512. Its totient is φ = 19274252.

The previous prime is 28911359. The next prime is 28911397. The reversal of 28911381 is 18311982.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 28911381 - 2¹⁴ = 28894997 is a prime.

It is a super-2 number, since 2×28911381² = 1671735902654322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28911301) 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 3 ways as a sum of consecutive naturals, for example, 4818561 + ... + 4818566.

It is an arithmetic number, because the mean of its divisors is an integer number (9637128).

Almost surely, 2^28911381 is an apocalyptic number.

It is an amenable number.

28911381 is a deficient number, since it is larger than the sum of its proper divisors (9637131).

28911381 is an equidigital number, since it uses as much as digits as its factorization.

28911381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9637130.

The product of its digits is 3456, while the sum is 33.

The square root of 28911381 is about 5376.9304440359. The cubic root of 28911381 is about 306.9184142366.

It can be divided in two parts, 28911 and 381, that added together give a palindrome (29292).

The spelling of 28911381 in words is "twenty-eight million, nine hundred eleven thousand, three hundred eighty-one".