221921 has 8 divisors (see below), whose sum is σ = 259200. Its totient is φ = 189924.

The previous prime is 221909. The next prime is 221941. The reversal of 221921 is 129122.

221921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 221921 - 2¹⁰ = 220897 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 221921.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221941) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20 + ... + 666.

It is an arithmetic number, because the mean of its divisors is an integer number (32400).

2²²¹⁹²¹ is an apocalyptic number.

It is an amenable number.

221921 is a deficient number, since it is larger than the sum of its proper divisors (37279).

221921 is an frugal number, since it uses more digits than its factorization.

221921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 668 (or 654 counting only the distinct ones).

The product of its digits is 72, while the sum is 17.

The square root of 221921 is about 471.0849180350. The cubic root of 221921 is about 60.5433061976.

The spelling of 221921 in words is "two hundred twenty-one thousand, nine hundred twenty-one".