28138871 has 4 divisors (see below), whose sum is σ = 28152192. Its totient is φ = 28125552.

The previous prime is 28138849. The next prime is 28138883. The reversal of 28138871 is 17883182.

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

It is a cyclic number.

It is not a de Polignac number, because 28138871 - 2¹⁰ = 28137847 is a prime.

It is a super-2 number, since 2×28138871² = 1583592122309282, 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 (28138801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2711 + ... + 7976.

It is an arithmetic number, because the mean of its divisors is an integer number (7038048).

Almost surely, 2^28138871 is an apocalyptic number.

28138871 is a deficient number, since it is larger than the sum of its proper divisors (13321).

28138871 is a wasteful number, since it uses less digits than its factorization.

28138871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13320.

The product of its digits is 21504, while the sum is 38.

The square root of 28138871 is about 5304.6084681152. The cubic root of 28138871 is about 304.1600863613.

The spelling of 28138871 in words is "twenty-eight million, one hundred thirty-eight thousand, eight hundred seventy-one".