165993 has 4 divisors (see below), whose sum is σ = 221328. Its totient is φ = 110660.

The previous prime is 165983. The next prime is 166013. The reversal of 165993 is 399561.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 399561 = 3 ⋅133187.

It is a cyclic number.

It is not a de Polignac number, because 165993 - 2⁵ = 165961 is a prime.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (165983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27663 + ... + 27668.

It is an arithmetic number, because the mean of its divisors is an integer number (55332).

2¹⁶⁵⁹⁹³ is an apocalyptic number.

It is an amenable number.

165993 is a deficient number, since it is larger than the sum of its proper divisors (55335).

165993 is an equidigital number, since it uses as much as digits as its factorization.

165993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55334.

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

The square root of 165993 is about 407.4223852466. The cubic root of 165993 is about 54.9578740790.

The spelling of 165993 in words is "one hundred sixty-five thousand, nine hundred ninety-three".