189217921 has 4 divisors (see below), whose sum is σ = 189245700. Its totient is φ = 189190144.

The previous prime is 189217907. The next prime is 189217927. The reversal of 189217921 is 129712981.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 11128896 + 178089025 = 3336^2 + 13345^2 .

It is a cyclic number.

It is not a de Polignac number, because 189217921 - 2⁷ = 189217793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (189217927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4065 + ... + 19873.

It is an arithmetic number, because the mean of its divisors is an integer number (47311425).

Almost surely, 2^189217921 is an apocalyptic number.

It is an amenable number.

189217921 is a deficient number, since it is larger than the sum of its proper divisors (27779).

189217921 is a wasteful number, since it uses less digits than its factorization.

189217921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27778.

The product of its digits is 18144, while the sum is 40.

The square root of 189217921 is about 13755.6505116988. The cubic root of 189217921 is about 574.0998351278.

The spelling of 189217921 in words is "one hundred eighty-nine million, two hundred seventeen thousand, nine hundred twenty-one".