28381987 has 4 divisors (see below), whose sum is σ = 28526256. Its totient is φ = 28237720.

The previous prime is 28381973. The next prime is 28382017. The reversal of 28381987 is 78918382.

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 28381987 - 2¹⁵ = 28349219 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28381907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 71839 + ... + 72232.

It is an arithmetic number, because the mean of its divisors is an integer number (7131564).

Almost surely, 2^28381987 is an apocalyptic number.

28381987 is a deficient number, since it is larger than the sum of its proper divisors (144269).

28381987 is a wasteful number, since it uses less digits than its factorization.

28381987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 144268.

The product of its digits is 193536, while the sum is 46.

The square root of 28381987 is about 5327.4747301137. The cubic root of 28381987 is about 305.0335428486.

The spelling of 28381987 in words is "twenty-eight million, three hundred eighty-one thousand, nine hundred eighty-seven".