387991 has 8 divisors (see below), whose sum is σ = 425520. Its totient is φ = 352128.

The previous prime is 387977. The next prime is 388009. The reversal of 387991 is 199783.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 387991 - 2¹¹ = 385943 is a prime.

It is a Duffinian number.

It is a plaindrome in base 11.

It is a self number, because there is not a number n which added to its sum of digits gives 387991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (387911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 100 + ... + 886.

It is an arithmetic number, because the mean of its divisors is an integer number (53190).

2³⁸⁷⁹⁹¹ is an apocalyptic number.

387991 is a deficient number, since it is larger than the sum of its proper divisors (37529).

387991 is a wasteful number, since it uses less digits than its factorization.

387991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 833.

The product of its digits is 13608, while the sum is 37.

The square root of 387991 is about 622.8892357394. The cubic root of 387991 is about 72.9357663526.

It can be divided in two parts, 387 and 991, that added together give a triangular number (1378 = T₅₂).

The spelling of 387991 in words is "three hundred eighty-seven thousand, nine hundred ninety-one".