365991 has 4 divisors (see below), whose sum is σ = 487992. Its totient is φ = 243992.

The previous prime is 365983. The next prime is 366001. The reversal of 365991 is 199563.

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 365991 - 2³ = 365983 is a prime.

It is a D-number.

It is a nialpdrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (365941) 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, 60996 + ... + 61001.

It is an arithmetic number, because the mean of its divisors is an integer number (121998).

2³⁶⁵⁹⁹¹ is an apocalyptic number.

365991 is a deficient number, since it is larger than the sum of its proper divisors (122001).

365991 is a wasteful number, since it uses less digits than its factorization.

365991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 122000.

The product of its digits is 7290, while the sum is 33.

The square root of 365991 is about 604.9719001739. The cubic root of 365991 is about 71.5303146267.

The spelling of 365991 in words is "three hundred sixty-five thousand, nine hundred ninety-one".