189821 has 4 divisors (see below), whose sum is σ = 192192. Its totient is φ = 187452.

The previous prime is 189817. The next prime is 189823. The reversal of 189821 is 128981.

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 189821 - 2² = 189817 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 (189823) 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, 1061 + ... + 1226.

It is an arithmetic number, because the mean of its divisors is an integer number (48048).

2¹⁸⁹⁸²¹ is an apocalyptic number.

It is an amenable number.

189821 is a deficient number, since it is larger than the sum of its proper divisors (2371).

189821 is an equidigital number, since it uses as much as digits as its factorization.

189821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2370.

The product of its digits is 1152, while the sum is 29.

The square root of 189821 is about 435.6845188895. The cubic root of 189821 is about 57.4709115630.

The spelling of 189821 in words is "one hundred eighty-nine thousand, eight hundred twenty-one".