28778181 has 4 divisors (see below), whose sum is σ = 38370912. Its totient is φ = 19185452.

The previous prime is 28778171. The next prime is 28778213. The reversal of 28778181 is 18187782.

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 28778181 - 2¹¹ = 28776133 is a prime.

It is a super-2 number, since 2×28778181² = 1656367403337522, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28778111) 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, 4796361 + ... + 4796366.

It is an arithmetic number, because the mean of its divisors is an integer number (9592728).

Almost surely, 2^28778181 is an apocalyptic number.

It is an amenable number.

28778181 is a deficient number, since it is larger than the sum of its proper divisors (9592731).

28778181 is an equidigital number, since it uses as much as digits as its factorization.

28778181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9592730.

The product of its digits is 50176, while the sum is 42.

The square root of 28778181 is about 5364.5298955267. The cubic root of 28778181 is about 306.4463455051.

The spelling of 28778181 in words is "twenty-eight million, seven hundred seventy-eight thousand, one hundred eighty-one".