817221 has 4 divisors (see below), whose sum is σ = 1089632. Its totient is φ = 544812.

The previous prime is 817211. The next prime is 817237. The reversal of 817221 is 122718.

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 not a de Polignac number, because 817221 - 2⁷ = 817093 is a prime.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

817221 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (817211) 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, 136201 + ... + 136206.

It is an arithmetic number, because the mean of its divisors is an integer number (272408).

2⁸¹⁷²²¹ is an apocalyptic number.

It is an amenable number.

817221 is a deficient number, since it is larger than the sum of its proper divisors (272411).

817221 is a wasteful number, since it uses less digits than its factorization.

817221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 272410.

The product of its digits is 224, while the sum is 21.

The square root of 817221 is about 904.0027654825. The cubic root of 817221 is about 93.4931601086.

Adding to 817221 its reverse (122718), we get a palindrome (939939).

The spelling of 817221 in words is "eight hundred seventeen thousand, two hundred twenty-one".