28891181 has 4 divisors (see below), whose sum is σ = 31517664. Its totient is φ = 26264700.

The previous prime is 28891171. The next prime is 28891189. The reversal of 28891181 is 18119882.

It is a happy number.

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 de Polignac number, because none of the positive numbers 2^k-28891181 is a prime.

It is a super-2 number, since 2×28891181² = 1669400679149522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28891189) 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, 1313225 + ... + 1313246.

It is an arithmetic number, because the mean of its divisors is an integer number (7879416).

Almost surely, 2^28891181 is an apocalyptic number.

It is an amenable number.

28891181 is a deficient number, since it is larger than the sum of its proper divisors (2626483).

28891181 is a wasteful number, since it uses less digits than its factorization.

28891181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2626482.

The product of its digits is 9216, while the sum is 38.

The square root of 28891181 is about 5375.0517206814. The cubic root of 28891181 is about 306.8469176355.

The spelling of 28891181 in words is "twenty-eight million, eight hundred ninety-one thousand, one hundred eighty-one".