309987 has 20 divisors (see below), whose sum is σ = 479160. Its totient is φ = 199584.

The previous prime is 309977. The next prime is 309989. The reversal of 309987 is 789903.

309987 is digitally balanced in base 7, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 309987 - 2⁸ = 309731 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

309987 is strictly pandigital in base 7.

It is a nialpdrome in base 9.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 309987.

It is not an unprimeable number, because it can be changed into a prime (309989) 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 19 ways as a sum of consecutive naturals, for example, 3439 + ... + 3527.

It is an arithmetic number, because the mean of its divisors is an integer number (23958).

2³⁰⁹⁹⁸⁷ is an apocalyptic number.

309987 is a deficient number, since it is larger than the sum of its proper divisors (169173).

309987 is an equidigital number, since it uses as much as digits as its factorization.

309987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 144 (or 135 counting only the distinct ones).

The product of its (nonzero) digits is 13608, while the sum is 36.

The square root of 309987 is about 556.7647618160. The cubic root of 309987 is about 67.6780484574.

It can be divided in two parts, 309 and 987, that added together give a 4-th power (1296 = 6⁴).

The spelling of 309987 in words is "three hundred nine thousand, nine hundred eighty-seven".