28781111 has 4 divisors (see below), whose sum is σ = 28792224. Its totient is φ = 28770000.

The previous prime is 28781101. The next prime is 28781141. The reversal of 28781111 is 11118782.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 28781111 - 2⁶ = 28781047 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28781101) 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, 611 + ... + 7611.

It is an arithmetic number, because the mean of its divisors is an integer number (7198056).

Almost surely, 2^28781111 is an apocalyptic number.

28781111 is a deficient number, since it is larger than the sum of its proper divisors (11113).

28781111 is an equidigital number, since it uses as much as digits as its factorization.

28781111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11112.

The product of its digits is 896, while the sum is 29.

The square root of 28781111 is about 5364.8029786750. The cubic root of 28781111 is about 306.4567452512.

Adding to 28781111 its reverse (11118782), we get a palindrome (39899893).

The spelling of 28781111 in words is "twenty-eight million, seven hundred eighty-one thousand, one hundred eleven".