189806821 has 4 divisors (see below), whose sum is σ = 193845312. Its totient is φ = 185768332.

The previous prime is 189806809. The next prime is 189806839. The reversal of 189806821 is 128608981.

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 189806821 - 2¹¹ = 189804773 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (189806801) 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, 2019175 + ... + 2019268.

It is an arithmetic number, because the mean of its divisors is an integer number (48461328).

Almost surely, 2^189806821 is an apocalyptic number.

It is an amenable number.

189806821 is a deficient number, since it is larger than the sum of its proper divisors (4038491).

189806821 is an equidigital number, since it uses as much as digits as its factorization.

189806821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4038490.

The product of its (nonzero) digits is 55296, while the sum is 43.

The square root of 189806821 is about 13777.0396312125. The cubic root of 189806821 is about 574.6948056517.

The spelling of 189806821 in words is "one hundred eighty-nine million, eight hundred six thousand, eight hundred twenty-one".