191921 has 8 divisors (see below), whose sum is σ = 204288. Its totient is φ = 180000.

The previous prime is 191911. The next prime is 191929. The reversal of 191921 is 129191.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-191921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (191929) 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 7 ways as a sum of consecutive naturals, for example, 1196 + ... + 1346.

It is an arithmetic number, because the mean of its divisors is an integer number (25536).

2¹⁹¹⁹²¹ is an apocalyptic number.

It is an amenable number.

191921 is a deficient number, since it is larger than the sum of its proper divisors (12367).

191921 is a wasteful number, since it uses less digits than its factorization.

191921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 223.

The product of its digits is 162, while the sum is 23.

The square root of 191921 is about 438.0878907251. The cubic root of 191921 is about 57.6820693855.

The spelling of 191921 in words is "one hundred ninety-one thousand, nine hundred twenty-one".