191021 has 2 divisors, whose sum is σ = 191022. Its totient is φ = 191020.

The previous prime is 190997. The next prime is 191027. The reversal of 191021 is 120191.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 148996 + 42025 = 386^2 + 205^2 .

It is a cyclic number.

It is not a de Polignac number, because 191021 - 2¹⁰ = 189997 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 190987 and 191005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (191027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95510 + 95511.

It is an arithmetic number, because the mean of its divisors is an integer number (95511).

2¹⁹¹⁰²¹ is an apocalyptic number.

It is an amenable number.

191021 is a deficient number, since it is larger than the sum of its proper divisors (1).

191021 is an equidigital number, since it uses as much as digits as its factorization.

191021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 18, while the sum is 14.

The square root of 191021 is about 437.0594925179. The cubic root of 191021 is about 57.5917627431.

The spelling of 191021 in words is "one hundred ninety-one thousand, twenty-one".