287991 has 12 divisors (see below), whose sum is σ = 453960. Its totient is φ = 174480.

The previous prime is 287977. The next prime is 288007. The reversal of 287991 is 199782.

It is a happy number.

It is not a de Polignac number, because 287991 - 2⁷ = 287863 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (287921) 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 11 ways as a sum of consecutive naturals, for example, 1356 + ... + 1553.

It is an arithmetic number, because the mean of its divisors is an integer number (37830).

2²⁸⁷⁹⁹¹ is an apocalyptic number.

287991 is a deficient number, since it is larger than the sum of its proper divisors (165969).

287991 is a wasteful number, since it uses less digits than its factorization.

287991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2926 (or 2923 counting only the distinct ones).

The product of its digits is 9072, while the sum is 36.

The square root of 287991 is about 536.6479292795. The cubic root of 287991 is about 66.0378570692.

Subtracting from 287991 its reverse (199782), we obtain a square (88209 = 297²).

The spelling of 287991 in words is "two hundred eighty-seven thousand, nine hundred ninety-one".