193991 has 12 divisors (see below), whose sum is σ = 233928. Its totient is φ = 160272.

The previous prime is 193979. The next prime is 193993. The reversal of 193991 is 199391.

It is a de Polignac number, because none of the positive numbers 2^k-193991 is a prime.

It is a Smith number, since the sum of its digits (32) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (193993) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1760 + ... + 1866.

It is an arithmetic number, because the mean of its divisors is an integer number (19494).

2¹⁹³⁹⁹¹ is an apocalyptic number.

193991 is a deficient number, since it is larger than the sum of its proper divisors (39937).

193991 is a wasteful number, since it uses less digits than its factorization.

193991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158 (or 151 counting only the distinct ones).

The product of its digits is 2187, while the sum is 32.

The square root of 193991 is about 440.4440940687. Note that the first 3 decimals coincide. The cubic root of 193991 is about 57.8887085067. Note that the first 3 decimals are identical.

The spelling of 193991 in words is "one hundred ninety-three thousand, nine hundred ninety-one".