28187881 has 4 divisors (see below), whose sum is σ = 28211200. Its totient is φ = 28164564.

The previous prime is 28187807. The next prime is 28187893. The reversal of 28187881 is 18878182.

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 a de Polignac number, because none of the positive numbers 2^k-28187881 is a prime.

It is a super-2 number, since 2×28187881² = 1589113270540322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28187801) 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, 9741 + ... + 12298.

It is an arithmetic number, because the mean of its divisors is an integer number (7052800).

Almost surely, 2^28187881 is an apocalyptic number.

It is an amenable number.

28187881 is a deficient number, since it is larger than the sum of its proper divisors (23319).

28187881 is a wasteful number, since it uses less digits than its factorization.

28187881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23318.

The product of its digits is 57344, while the sum is 43.

The square root of 28187881 is about 5309.2260264562. The cubic root of 28187881 is about 304.3365710499.

The spelling of 28187881 in words is "twenty-eight million, one hundred eighty-seven thousand, eight hundred eighty-one".