28775881 has 4 divisors (see below), whose sum is σ = 28842772. Its totient is φ = 28708992.

The previous prime is 28775867. The next prime is 28775909. The reversal of 28775881 is 18857782.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4372281 + 24403600 = 2091^2 + 4940^2 .

It is a cyclic number.

It is not a de Polignac number, because 28775881 - 2⁷ = 28775753 is a prime.

It is a super-2 number, since 2×28775881² = 1656102654652322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28775821) 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, 32796 + ... + 33661.

It is an arithmetic number, because the mean of its divisors is an integer number (7210693).

Almost surely, 2^28775881 is an apocalyptic number.

It is an amenable number.

28775881 is a deficient number, since it is larger than the sum of its proper divisors (66891).

28775881 is an equidigital number, since it uses as much as digits as its factorization.

28775881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66890.

The product of its digits is 250880, while the sum is 46.

The square root of 28775881 is about 5364.3155201759. The cubic root of 28775881 is about 306.4381813874.

The spelling of 28775881 in words is "twenty-eight million, seven hundred seventy-five thousand, eight hundred eighty-one".