189999721 has 4 divisors (see below), whose sum is σ = 190756944. Its totient is φ = 189242500.

The previous prime is 189999707. The next prime is 189999731. The reversal of 189999721 is 127999981.

189999721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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.

It is a cyclic number.

It is not a de Polignac number, because 189999721 - 2⁹ = 189999209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (189999731) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 378235 + ... + 378736.

It is an arithmetic number, because the mean of its divisors is an integer number (47689236).

Almost surely, 2^189999721 is an apocalyptic number.

It is an amenable number.

189999721 is a deficient number, since it is larger than the sum of its proper divisors (757223).

189999721 is an equidigital number, since it uses as much as digits as its factorization.

189999721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 757222.

The product of its digits is 734832, while the sum is 55.

The square root of 189999721 is about 13784.0386316928. The cubic root of 189999721 is about 574.8894265010.

The spelling of 189999721 in words is "one hundred eighty-nine million, nine hundred ninety-nine thousand, seven hundred twenty-one".