921221 has 8 divisors (see below), whose sum is σ = 1064064. Its totient is φ = 781200.

The previous prime is 921203. The next prime is 921223. The reversal of 921221 is 122129.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 921221 - 2⁶ = 921157 is a prime.

It is an Ulam number.

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 921221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (921223) 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, 56 + ... + 1358.

It is an arithmetic number, because the mean of its divisors is an integer number (133008).

2⁹²¹²²¹ is an apocalyptic number.

It is an amenable number.

921221 is a deficient number, since it is larger than the sum of its proper divisors (142843).

921221 is a wasteful number, since it uses less digits than its factorization.

921221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1411.

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

The square root of 921221 is about 959.8025838682. The cubic root of 921221 is about 97.3018900853.

The spelling of 921221 in words is "nine hundred twenty-one thousand, two hundred twenty-one".